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The reliable identification of biosignatures is key to the search for life elsewhere. On ocean worlds like Enceladus or Europa, this can be achieved by impact ionization mass spectrometers, such as the SUrface Dust Analyzer (SUDA) on board NASA's upcoming Europa Clipper mission. During spacecraft flybys, these instruments can sample ice grains formed from subsurface water and emitted by these moons. Previous laboratory analog experiments have demonstrated that SUDA-type instruments could identify amino acids, fatty acids, and peptides in ice grains and discriminate between their abiotic and biotic origins. Here, we report experiments simulating impact ionization mass spectra of ice grains containing DNA, lipids, and metabolic intermediates extracted from two bacterial cultures

Events which deposit fresh material onto Europa’s surface may be irregular and catastrophic, such as large-scale impacts, or localized, and potentially extant, processes in which faults, fractures, or brine transport bring subsurface liquid onto the surface. This liquid may originate from shallow reservoirs within the ice shell or directly from the subsurface ocean [1]. Emplacement may be a slow, extrusive process, or quicker, potentially with the formation of cryovolcanic plumes (e.g. [2,3,4]). Plume deposits or any other surface material can also be transported to high altitudes by another mechanism: when hypervelocity interplanetary micrometeoroids, or larger objects, impact the surface of an atmosphereless planetary body like Europa, these can generate impact ejecta with high enough velocities to reach altitudes of hundreds of kilometres [5]. Most of these ejecta particles are gravitationally bound, moving on ballistic trajectories lasting up to hundreds of seconds and producing an almost isotropic dust exosphere around Europa [6,7]. Subsurface oceans, in the Jovian and in other planetary systems, can therefore be characterized using the particles they emit, via either indirect or direct routes: 1) Detection and analysis of ejecta particles lofted by micrometeoroid impacts from those parts of the surface that recently interacted with subsurface water (e.g. certain landforms, such as chaos terrains on Europa, or plume deposits); 2) Direct sampling of plume particles in space (where plumes are present, as perhaps possible on Europa). The SUrface Dust Analyzer (SUDA), onboard the Europa Clipper spacecraft, is designed to measure the composition and trajectories of such impact ejecta particles and/or plume material. SUDA is an impact ionisation time-of-flight mass spectrometer, which uses the ions generated by hypervelocity impacts of dust grains onto the instrument target to generate mass spectra of the impinging particles. Depending on the altitude, SUDA will be able to detect up to tens of ejected surface particles per second during each flyby, each likely to contain a wide variety of organic and/or inorganic compounds, and via trajectory reconstruction, map them to their origins on the surface [8]. At global scales, landform evolution on atmosphereless bodies is primarily driven by impact gardening and tectonics. The tectonic regime that dominates within Europa’s ice shell is likely to be extensional, a hypothesis supported by numerous lines of evidence, such as the widespread presence of dilational bands that represent >40% of the total surface area [9]. Several types of geological features generated within such a tectonic regime, including chaos terrains and fossae, might affect the emplacement of buried material and subsequent exposure of fresh volatiles on Europa’s surface. Chaos Terrains are, on Europa, geologically very young and extensively disrupted surface features, interpreted as reflecting recent interaction with subsurface material [10]. Leading-hemisphere chaos regions have recently been shown to be compositionally distinct from their surroundings, probably indicating contributions from endogenous sodium chloride sourced from the subsurface ocean [11,12]. Fossae are long, narrow depressions (troughs). The term is used for topographic features that occur on extraterrestrial planetary surfaces, whose exact origin is uncertain, although they are thought to be the result of extensional tectonic processes [13]. Here we investigate two neighboring features on Europa, Ménec Fossae and Thrace Macula (a chaos terrain), for which we produced high-resolution photoclinometrically-derived [14] digital terrain models (DTMs, Fig. 1) and geomorphological-structural maps (Fig. 2). Our preliminary results suggest that this area of Europa has undergone transtensional (strike-slip paired with extension) tectonic activity, as indicated by the orientation and relationship of the faults and fossae. Such tectonic style has possibly created a pathway facilitating the ascent of subsurface material, especially volatiles, that play an important role in the formation of chaos terrain. These results will help ascertain the most likely regions on Europa in which to find fresh material, representative of the subsurface ocean, and be used as input data for dust ejecta trajectory models that will ultimately assist the mass spectrometer Surface Dust Analyzer (SUDA), onboard the upcoming Europa Clipper mission, in compositionally mapping Europa’s surface [15]. Figure 1. Regional DTMs, Ménec Fossae (top) and Thrace Macula (bottom) Figure 2. Geomorphological map of Ménec Fossae 1. Head, J.W., & Pappalardo, R.T., (1999). J. Geophys. Res. 104, 27143–27155. 2. Roth, L., et al., (2014). Science 343, 171. 3. Sparks, W.B., et al., (2017). The Astrophysical Journal Letters, 839(2), L18. 4. Jia, X., et al., (2018). Nat. Astron. 2, 459. 5. Koschny, D., & Grün, E., (2001). Icarus, 154(2), 402-411. 6. Krivov, A. V., et al., (2003a). Planetary and Space Science 51, 251-269. 7. Postberg, F., et al., (2011). Planetary and Space Science, 59(14), 1815–1825. 8. Goode, W., et al., (2021). Planetary and Space Science, 208, 105343 9. Kattenhorn, S.A. & Hurford, T.A., (2009). In: Europa, 199-236. 10. Schmidt, B. E., et al., (2011). Nature 502, v. 479 11. Trumbo, S. K., et al., (2019). SciA, 5, aaw7123 12. Trumbo, S. K., et al., (2022), PSJ, 3, 27 13. Schenk, P., et al., (2020). Geophys. Res. Let., 47, e2020GL088364 14. Lesage et al., (2021). Icarus, Volume 361, 114373. 15. Kempf, S., et al., (2019). AGU Fall Meeting 2019, abstract #P53D-3500

Measurements during the final phase of the Cassini mission revealed the composition of individual dust particles, ejected by micrometeoroid impacts from Saturn’s main rings. These measurements were conducted with the in situ time-of-flight mass spectrometer of the Cosmic Dust Analyzer (CDA) [1] during the close planet encounters of the Grand Finale Orbits from April to September of 2017.Here we present the compositional analysis of silicate bearing nanoparticles (about 20–100 nm in radius), that, according to our dynamical models [2], are ejected mainly from the B and C rings by micrometeoroid impacts. With an observed ice-to-silicate particle ratio of 2:1 [2], we see a much higher silicate abundance in these ring segments, compared to values constrained by remote sensing techniques [3,4,5].In order to assess the elemental composition of individual particles, application of a deconvolution technique to the CDA mass spectra is required. This technique is based on an approach to constrain the composition of Interstellar Dust Particles (ISDs), also detected with CDA [6]. After application of the deconvolution and Relative Sensitivity Factors (RSFs) [7], elemental abundances for the individual particles are derived.We find Mg, Si and Ca similar to cosmic abundances (ISD and CI chondritic). Fe, however, is significantly depleted, for the Fe/Mg ratio on average by a factor of 2.3 compared to cosmic abundances. This observation contrasts with Fe-rich (≈ 5 w.r.t. cosmic abundances) exogenous material (IDPs), observed in the Saturnian system by CDA [8]. This drastic discrepancy in composition between ring silicates and IDPs at Saturn seems difficult to reconcile with IDPs being the main factor in polluting and darkening the rings over time [4,5,9,10]. We review several scenarios, how these compositional differences could be explained. References[1] R. Srama et al. (2004), Space Science Reviews 114, 465–518.[2] H.-W. Hsu et al. (2018), Science 362.[3] E. Epstein et al. (1984), Icarus 58, 403–411.[4] Zhang et al. (2017a), Icarus 281, 297–321.[5] Zhang et al. (2017b), Icarus 294, 14–42.[6] N. Altobelli et al. (2016), Science 352, 312–318.[7] K. Fiege et al. (2014), Icarus 241, 336–345.[8] C. Fischer et al. (2022), this conference.[9] J. Cuzzi and P. Estrada (1998), Icarus 132, 1–35.[10] J. Cuzzi et al. (2009), Springer, Dordrecht, 459–509.

Introduction The reliable identification and quantification of biosignatures on extraterrestrial ocean worlds is key to the search for life in our Solar System. Saturn’s moon Enceladus, and potentially Jupiter’s moon Europa, emit plumes of gas and ice grains formed from subsurface water into space (Spahn et al. 2006, Roth et al. 2014). The ice grains can be sampled during spacecraft flybys by impact ionization mass spectrometers, such as the Cosmic Dust Analyzer (CDA; Srama et al. 2004) on board the past Cassini mission, the SUrface Dust Analyzer (SUDA; Kempf et al. 2014) on board the upcoming Europa Clipper mission (Howell & Pappalardo 2020), or the ENceladus Ice Analyzer (ENIA), proposed for future Enceladus missions (Reh et al. 2016). CDA data collected in the Saturnian System revealed that Enceladus’s ocean is salty (Postberg et al. 2009) and contains a variety of organic material, including complex macromolecules (Postberg et al. 2018) as well as low-mass volatile compounds (Khawaja et al. 2019), some of which could potentially act as amino acid precursors. Our recent detection of phosphates in ice grains emitted by Enceladus (Postberg et al. 2022) further enhances Enceladus’s potential as a habitable environment, possibly able to support microbial life in its subsurface ocean. However, biosignatures have not yet been identified on extraterrestrial ocean worlds. Impact ionization detectors, such as SUDA or ENIA, are the only instruments capable of determining the compositions of single µm-sized ice grains emitted into plumes. Cassini CDA results showed that refractory organics occur in only a few % of plume ice grains. These are thought to form from an organic film covering the oceanic surface (Postberg et al., 2018). Cell material, if present, would likely reside in such grains and would only be present in an even smaller number of ice grains, maybe just one in a thousand or less. On Earth, 70% of the planetary surface is covered by a biofilm, the surface microlayer on top of the ocean water (Flemming and Wuertz, 2019), which hosts a distinct microbial community at cell densities 3 – 5 orders of magnitude higher than in the bulk water phase (Franklin et al. 2005). After lifting, organics and cells from this layer can initiate ice crystal formation in clouds (Pratt et al. 2009). Methods and Results To simulate such a scenario, where biosignatures are only present in a small fraction of emitted grains, but with a high cell density, we conducted laboratory analogue experiments with Sphingopyxis alaskensis, an ultrasmall bacterium, extracted from various cold marine environments (Ting et al. 2010) and potentially capable of fitting into µm-sized ice grains. We simulated the case of an ice grain of 15µm in diameter - constituting the worst case for Enceladus where ice grains are generally much smaller (1-5 µm in diameter) - formed from a nucleation core of one single bacterial cell. We used Laser Induced Liquid Beam Ion Desorption (LILBID) – a proven technique to simulate accurately impact ionization mass spectra of ice grains recorded in space (Klenner et al. 2019, 2020, 2020a). Recent LILBID experiments predict that DNA and lipids extracted from bacterial cultures will produce characteristic signals in the mass spectra of ice grains emitted from ocean worlds (Dannenmann et al. 2022, under review). Here we present the next steps – LILBID experiments with otherwise untreated lysed bacterial cells simulating the appearance of these microbial life forms in impact ionization mass spectra. In both polarity mass spectra, we clearly identify signatures of S. alaskensis. Cation mass spectra exhibit features due to protonated amino acids, either fragments of the bacteria’s proteins or metabolic intermediates. Deprotonated fatty acids, fragments of bacterial lipids, are identifiable in anion mass spectra. Our experiments show that even if less than 0.1% of the cell constituents would form a nucleation core of a 15µm ice grain, the bacterial signature would be apparent in the data. The recorded spectra are part of a comprehensive database containing analogue data for impact ionization mass spectrometers on board spacecraft (Klenner et al. 2022, under review). Conclusions Our results show that biosignatures deriving from a single bacterial cell – or small fractions of it - embedded as a nucleation core in an ice grain will be clearly identifiable in impact ionization mass spectra from SUDA-type instruments. This demonstrates the advantage of analyzing individual ice grains in a plume over analyzing the average composition of all plume material encountered during a flyby. A modern impact ionization instrument like SUDA or ENIA would be capable of recording 10,000 – 100,000 ice grain spectra (cations and anions) during a single plume passage, allowing to assess biosignatures that are present in only 1 out of 100,000 grains during a multiple flyby mission. Such low abundances would be out of reach for other analytical methods that measure the integrated - and thus extremely diluted - concentrations of such biosignatures in a plume. References Dannenmann, M. et al. (2022) Astrobiology, under review. Flemming, H.-C. & Wuerz, S. (2019) Nat Rev Microbiol 17, 247–260. Franklin, M.P. et al. (2005) Environ Microbiol 7, 723–736. Howell, S.M. & Pappalardo, R.T. (2020) Nat Commun 11, 1311. Kempf, S. et al. (2014) EPSC 9, EPSC2014–229. Khawaja, N. et al. (2019) Mon Not R Astron Soc 489, 5231–5243. Klenner, F. et al. (2019) Rapid Commun Mass Spectrom 33, 1751–1760. Klenner, F. et al. (2020a) Astrobiology 20, 179–189. Klenner, F. et al. (2020b) Astrobiology 20, 1168–1184. Klenner, F. et al. (2022) Earth Space Sci, under review. Postberg, F. et al. (2009) Nature 459, 1098–1101. Postberg, F. et al. (2018) Nature 558, 564–568. Postberg, F. et al. (2022) AbSciCon Abstract, 505-01. Pratt, K.A. et al. (2009) Nat Geosci 2, 398–401. Reh, K. et al (2016) IEEE AeroConf Abstract, 1–8. Roth, L. et al. (2014) Science 343, 171–174. Spahn, F. et al. (2006) Science 311, 1416–1418. Srama, R. et al. (2004) Space Sci Rev 114, 465–518. Ting, L. et al. (2010) Environ Microbiol 12, 2658–267.

Rare presolar grains originating by condensation in circumstellar atmospheres are known from meteorites [1]. These escaped processing in the solar nebula and are identified via their extremely diverse isotopic composition [1,2]. However, it is uncertain if such grains are representative for dust from the interstellar medium (ISM) [3–5], particular as [5] postulated a high fraction of interstellar grain population that formed directly in the ISM.In 1992 the Ulysses spacecraft discovered a dust flow from the Local Interstellar Cloud (LIC) [6]. During the Cassini mission at Saturn, the Cosmic Dust Analyser (CDA) could identify and analyse the chemical composition of 36 individual interstellar dust (ISD) particles [7]. These grains were distinguished from Saturn bound dust by their direction and high velocity. Their mean mass is consistent with the typical size [3-5] derived from astronomical observations. As major result, each individual ISD grain contains the major rock forming elements (Mg, Si, Fe, Ca) in roughly cosmic abundances, indicating compositional homogeneity at spatial scales as small as 100 nm. In contrast, CDA did neither detect carbon-rich grains such as graphite or SiC, nor pure metal grains (upper limit of 8% at the 2 sigma confidence level) [7].This homogeneity cannot be reconciled with isotopically and compositionally diverse populations of circumstellar dust inherited from AGB stars and supernovae found in meteorites. These grain populations consist mainly of silicates with a more diverse composition (e.g., olivine, pyroxene), however, also minor contributions (few %) of Al-oxides (e.g., corundum, hibonite), as well as carbonaceous grains (mainly silicon carbide) which contribute 20-50%, of the grains in the most primitive meteorites [2]. In contrast to circumstellar grains found in meteorites, the LIC-ISD grains detected by Cassini have a much lower variation of Mg/Si or Mg/Fe ratios [7], and appear to be a grain population homogenized by destruction, recondensation and equilibration processes in the ISM. This can be reconciled with astronomical observations of the diffuse ISM demonstrating that condensable elements of atomic mass >23 are depleted in the gas phase and hence bound in solids. Considering that the mean lifetime of ISD grains against destruction by supernova shocks is much shorter (c. 0.5 Ga) than the average residence time of ISM matter of 2.5 Ga [5], an origin of a high fraction of ISD by grain destruction followed by recondensation was suggested by [5,7]. While grain destruction most likely occurs in the hot interstellar medium, i.e., low-density cavities formed by supernova shock fronts, condensation likely occurs in the cold interstellar medium, i.e., cold molecular clouds which are also formation regions of stars and planets.The upcoming DESTINY+ mission [8] will be equipped with an improved impact ionization mass spectrometer, the DESTINY+ Dust Analyser (DDA). During the mission, hundreds of ISD particles are expected to be measured [9]), yielding high quality mass spectra with a resolution of c. 100-200 when compared to c. 20-50 of Cassini CDA [10]. This will allow much better resolution of mass peaks at 23-28 amu (Na, Mg, Al, Si) and 39-41 (K, Ca), particularly yielding improved constraints on abundances of Al and Si. This will allow, e.g., to distinguish between Mg silicates like pyroxene and olivine or Al-rich feldspar type silicates. Also, more precise values for Na and K can be expected, particularly as some of the Cassini CDA data were compromised by alkali contamination of the Rhodium target [7]. Furthermore, the higher number of ISD particle detections will allow to better quantify the ISD fraction of non-silicate particles (oxides, SiC, graphite, metal, see [1]). This will also provide constraints on dynamic forces acting on the ISD particle flux, particularly the question if high beta particles are preferentially deflected from the inner solar system by solar radiation forces. Finally, DDA measurements will also contribute to solve the problem of apparently low or “missing” organic components in CDA detected particles, which may be caused by volatilization of refractory organic material in ISD mantles upon entering the heliosphere [11].Hence, interstellar dust detections by the DESTINY+ Dust Analyser will likely improve our understanding of the chemical nature of interstellar dust, its processing and lifetime in various phases of the interstellar medium, possible processing and volatile loss upon traversing our solar system to 1 AU, flux modulations upon interaction with solar electromagnetic forces, and last but not least, a tight age constraint on the LIC dust. References:[1] E. Zinner (2014) In Meteorites and Cosmochemical Processes (ed. Davis A. M.). Elsevier, Amsterdam, pp. 181–213[2] J. Leitner, C. Vollmer, P. Hoppe, J. Zipfel (2012) Astrophysical Journal 745, 38[3] P. C. Frisch et al. (1999) Astrophysical Journal 525, 492[4] H. Kimura, I. Mann, E. K. Jessberger (2003) Astrophysical Journal 583, 314[5] S. Zhukovska, H.-P. Gail, M. Trieloff (2008) Astronomy & Astrophysics 479, 453[6] E. Grün et al. (1993) Nature 362, 428-430[7] N. Altobelli, F. Postberg, K. Fiege, M. Trieloff et al. (2016) Science 352, 312[8] H. Arai, M. Kobayashi, et al. (2018) Lun. Planet. Sci. Conf. 49, abstr. #2570[9] Krüger H., Strub P., et al. (2019) Planetary & Space Science 172, 22-42.[10] Srama R. et al. (2004) Space Science Reviews 114, 465-518. [11] H. Kimura, F. Postberg, N. Altobelli, M. Trieloff (2020) Astronomy & Astrophysics 643, A50

Mass spectrometers on board spacecraft typically use either impact ionization or electron ionization (EI) as ion sources. Understanding the similarities and differences in the spectral signatures and fragmentation patterns produced by different techniques in mass spectrometry could elucidate the composition of organic compounds. Here we present a comparison between the mass spectra obtained through laser-induced liquid beam ion desorption (LILBID; proven to simulate the impact ionization mass spectra of ice grains) and EI mass spectra of pairs of low-mass, isomeric aldehydes and ketones. Our comparison confirms that EI produces more fragmentation of carbonyl compounds, particularly aldehydes, than LILBID. We find protonated molecular ions [M+H]+ in LILBID but molecular ions [M]+ in EI spectra. From the evaluated species, LILBID generally produces oxygen-carrying fragment ions (e.g., [CHO]+ and [C2H3O]+) in the mass ranges 26–30 and 39–44 u, while in EI, most ions in these ranges correspond to hydrocarbon fragments. The LILBID spectra additionally show mostly protonated oxygen-bearing fragments [CH3O]+ and [C2H5O]+ at m/z 31 and 45, less commonly observed in EI spectra. We observe a decrease in the relative intensities of cation fragment mass lines between m/z 26 and 33 and an increase between m/z 39 and 45, with an increasing carbon number for ketones and aldehydes with LILBID and EI, respectively. Our study provides a basis for complementary compositional analysis to identify the structural properties of organic species in a space environment using different spaceborne mass spectrometers (e.g., SUrface Dust Analyzer and MAss Spectrometer for Planetary EXploration) on board NASA’s future Europa Clipper space mission.

Long-term changes in average temperatures, precipitation, and climate variability threaten agricultural production, food security, and the livelihoods of farming communities globally. Whilst adaptation to climate change is necessary to ensure food security and protect livelihoods of poor farmers, mitigation of greenhouse gas (GHG) emissions can lessen the extent of climate change and future needs for adaptation. Many agricultural practices can potentially mitigate GHG emissions without compromising food production. India is the third largest GHG emitter in the world where agriculture is responsible for 18% of total national emissions. India has identified agriculture as one of the priority sectors for GHG emission reduction in its Nationally Determined Contributions (NDCs). Identification of emission hotspots and cost-effective mitigation options in agriculture can inform the prioritisation of efforts to reduce emissions without compromising food and nutrition security.We adopted a bottom-up approach to analyse GHG emissions using large datasets of India's ‘cost of cultivation survey’ and the ‘19th livestock census’ together with soil, climate and management data for each location. Mitigation measures and associated costs and benefits of adoption, derived from a variety of sources including the literature, stakeholder meetings and expert opinion, were presented in the form of Marginal Abatement Cost Curves (MACC). We estimated that by 2030, business-as-usual GHG emissions from the agricultural sector in India would be 515 Megatonne CO2 equivalent (MtCO2e) per year with a technical mitigation potential of 85.5 MtCO2e per year through adoption of various mitigation practices. About 80% of the technical mitigation potential could be achieved by adopting only cost-saving measures. Three mitigation options, i.e. efficient use of fertilizer, zero-tillage and rice-water management, could deliver more than 50% of the total technical abatement potential.

The Cassini-Huygens space mission investigated Saturn, its ring system and moons for 13 years, with outstanding results [1]. Cassini’s mass spectrometers — the Cosmic Dust Analyzer (CDA) [2] and the Ion & Neutral Mass Spectrometer (INMS) [3] — contributed to many breakthrough discoveries, confirming mass spectrometry to be a reliable analytical tool for investigating planetary bodies and their vicinities [4]. Compositional analysis of micron and sub-micron sized dusty grains was undertaken by the CDA, an impact ionization time of flight mass spectrometer. Particles striking the instrument’s metal target at speeds ≥ ~1 km/s were disrupted, vaporized and partially ionized. The generated cations were accelerated toward the instrument’s detector to produce mass spectra with resolutions of (m/∆m) ~20-50 [2]. With the limited mass resolution, CDA revealed subsurface hydrothermal activity [5] on Enceladus and discovered potential biologically-relevant complex [6] as well as volatile organic [7] in ice grains emerging from Enceladus subsurface ocean. A more recent, higher performance, spacecraft-borne impact ionization mass spectrometer — the SUrface Dust Analyzer (SUDA) [8] — will be a part of NASA’s Europa Clipper mission to explore the habitability of Jupiter’s moon Europa. To calibrate these instruments, terrestrial analogue experiments are needed. In contrast to impact ionization, some soft ionization mass spectrometric techniques use a matrix to protect the structure of analyte molecules. These techniques include Matrix-Assisted Laser Desorption Ionization (MALDI) and Laser Induced Liquid Beam Ion Desorption (LILBID), which primarily use 2,5- or 2,3-dihydroxybenzoic acid (DHBA) [9], and water [10] as matrix substances, respectively. Although MALDI is by far the more common laboratory technique used for the analysis and the detection of biomolecules [11], LILBID is proven to accurately simulate impact ionization mass spectra of water ice grains [6][7][10]. In LILBID, a thin micrometer-scale liquid water beam, containing analyte compounds, is injected into a vacuum and irradiated by a pulsed infrared laser. Due to the laser’s energy, the solvent together with the analyte compounds are explosively dispersed, ionized and fragmented, generating a cloud of cations, anions, electrons, and neutrals [12][10]. The cations or anions (and electrons) can then be analyzed in a commercial time-of-flight mass spectrometer. A wide variety of compounds have been measured with the LILBID setup, to assist in the ongoing interpretation of CDA mass spectra, and predict those expected from SUDA in situ (cationic & anionic) mass spectra, thus inferring the composition of ice grains ejected from Enceladus’ or Europa’s oceans respectively. Laboratory campaigns, using the LILBID apparatus to generate mass spectra of a wide range of both inorganic and organic compounds, are ongoing. The data produced forms an expanding database, from which methodologies and rules for LILBID (and therefore impact ionization) mass spectral interpretation are being developed, in preparation for application to future missions [13]. Here, we present a comparison between the LILBID mass spectra of benzoic acid (C6H5COOH) and its derivative compounds: 2,5- & 2,3-DHBA (C7H6O4). In this work, we study with our LILBID setup the correlation between fragmentation behaviour of these aromatic acids and the position of hydroxy functional groups (at aromatic ring). These compounds share common structural features including one benzene ring and one carboxylic functional group. However, the dihydroxybenzoic acids have two hydroxyl groups attached at different carbon positions on the aromatic ring (2 and 5 or 2 and 3). We observe the same fragmentation pattern and features in the LILBID spectra of both DHBA compounds, indicating that the exact positions of the hydroxy functional groups have no impact on the mass spectral features. However, when comparing benzoic acid with its derivatives (2,5-DHBA & 2,3-DHBA), we find characteristic differences in their spectral signatures probably due to the attached hydroxy functional groups to the aromatic ring of these compounds. These data will be applied to the interpretation of CDA mass spectra of organic containing grains emitted from Enceladus, in which hitherto unidentified aromatic compounds have already been detected [6][7]. Understanding the behaviour of aromatic acids (e.g. benzoic acid) in comparison with its hydroxy derivatives (2,5-DHBA & 2,3-DHBA) under conditions which simulate impact ionization also relevant for the interpretation of unique results that will be produced by spaceborne mass spectrometers such as SUDA [8] onboard NASA’s future Europa Clipper mission. References [1] P. M. Schenk et al. (2018) Uni. of Arizona Press, Tucson, AZ [2] R. Srama et al. (2004) Space Sci Rev. 114:465-518 [3] J. H. Waite et al. (2006) Science 311(5766) 1419-1422 [4] Jr. A. Ricardo, N. Ziqin & D. M. Ryan (2019) Journal of Mass Spectrometry Vol. 55 [5] Hsu et al. (2005) Nature 519.7542: 207-210 [6] Postberg et al. (2018) Nature 558:564–568 [7] Khawaja et al. (2019) Mon. Not. R. Astron. Soc. 489:5231–5243 [8] Kempf et al. (2014) EPSC2014-229, 2014 [9] W.E. Wallace, M.A. Arnould, R. Knochenmuss (2005) Int. Jour. Of Mass Spectrom. 242: 13-22 [10] Klenner et al. (2019) Rapid Commun Mass Spectrom. 33.22: 1751-1760 [11] L. Ling et al. (2018) J. Am. Soc. Mass Spectrom. 29:704-710 [12] F. Wiederschein et al. (2015) Royal Society of Chemistry 17, 6858 [13] Klenner et al. (2021; in preparation)

Mass spectra from the Cosmic Dust Analyzer (CDA) [1] onboard the Cassini spacecraft revealed the existence of different compositional types of icy dust particles in Saturn’s E-ring. Most of these µm to sub-µm water ice grains were ejected from the cryo-volcanoes at the southern polar region of Enceladus and carry different constituents, for example organic compounds or salts [2-5]. These particles are subject to ongoing plasma sputtering during their lifetime in the E-ring [6,7]. Recent modelling of the dynamics of E-ring particles has shown that, in the region between the orbital distances of Dione and Rhea, the outwards migration of a proportion of the E-ring dust slows down and almost comes to a halt [8]. Due to the minimum of the V-shaped electrostatic grain equilibrium potential [9] and a polarity reversal of the dust surface charges [10], the semi-major axes of the dust particles’ orbits actually stop growing, forcing the particles to spend a significant part of their lifetime at this distance from Saturn. Therefore, this phenomenon should allow plasma sputtering to operate much longer on the dust particles residing in this region, potentially resulting in detectable alterations to the dust particle properties, e.g. particle composition and size, in this region. Here we present the discovery of a new population of grains within the E ring, which show signs of compositional alteration, best explained by plasma sputtering. The radial frequency distribution of these grains shows a distinct accumulation in the region between the orbits of Dione and Rhea, and may provide evidence of prolonged residence there. Analyses of CDA mass spectra of the grains, interpreted via comparison with laboratory Laser‐Induced Liquid Beam Ion Desorption (LILBID) [11] analogue experiments, indicate the particles to be very salt-rich water ice. In comparison to the previously reported salt-rich particle types, generated from Enceladus’ subsurface ocean [3,4] this new population must possess a far higher salt concentration to explain its observed spectral appearance. We propose that the increase in salt concentration arises from sputtering-induced removal of water from less salty oceanic grains (Type 3) [3,4], during their extended time in the region between Dione and Rhea. This population may therefore represent the first confirmation of the proposed dynamical barrier within Saturn’s E-ring. References [1] Srama, R. et al., The Cassini Cosmic Dust Analyzer, Space Science Reviews, 114, 465-518, 2004. [2] Hillier, J. et al., The composition of Saturn’s E ring, Mon. Not. R. Astron. Soc., 377, 1588–1596, 2007 [3] Postberg, F. et al., The E-ring in the vicinity of Enceladus II. Probing the moon’s interior-The composition of E-ring particles, Icarus, 193, 438-454, 2008. [4] Postberg, F. et al., Sodium salts in E-ring ice grains from an ocean below the surface of Enceladus, Nature, 459, 1098-1101, 2009. [5] Postberg, F. et al., A salt-water reservoir as the source of a compositionally stratified plume on Enceladus, Nature, 474, 620–622, 2011 [6] Jurac, S. et al., Saturn’s E Ring and Production of the Neutral Torus, Icarus, 149, 384–396, 2001 [7] Johnson, R. E. et al., Sputtering of ice grains and icy satellites in Saturn’s inner magnetosphere, Planetary and Space Science, 56, 1238–1243, 2008 [8] Kempf & Beckmann, Dynamics and long-term evolution of Saturn's E ring particles (in prep.) [9] Mitchell, C. J. et al., Tenuous ring formation by the capture of interplanetary dust at Saturn, JOURNAL OF GEOPHYSICAL RESEARCH, 110, 2005 [10] Kempf, S. et al., The electrostatic potential of E ring particles, Planetary and Space Science, 54, 999-1006, 2006 [11] Klenner, F. et al., Analogue spectra for impact ionization mass spectra of water ice grains obtained at different impact speeds in space, Rapid Commun Mass Spectrom., 33, 1751–1760, 2019

During the final mission phase, the Cassini spacecraft travelled through the gap between Saturn and its innermost D ring. One goal of these highly inclined orbits was sampling the dust population, mostly made of impact ejecta from the main rings, in the vicinity of the planet. These in situ measurements were primarily carried out by the Cosmic Dust Analyzer (CDA) onboard the spacecraft, which provided time-of-flight mass spectra of individual ice and dust grains, mostly between about 10 and 50 nm in size. Here we present an update on the composition of the silicate dust fraction stemming from Saturn’s main rings, which makes up about 30 % of the observed particles with water ice being the remaining fraction [1]. Elemental analysis of the silicate spectra was performed using an updated deconvolution method, based on a technique originally applied to the interpretation of CDA interstellar dust measurements [2]. Neighboring spectral peaks due to mineral-forming ions such as Mg+, Al+ and Si+ are often unresolvable, because of CDA’s relatively low (m/dm = 20–50) mass resolution [3]. Therefore, application of a deconvolution technique is required to disentangle the peak interferences and derive valuable compositional information. The robustness of the applied method has been tested and optimized through comparison with an independent automated fit algorithm. In order to calculate elemental abundances within the particles, the derived ion abundances were combined with experimentally-determined relative sensitivity factors (RSFs) [4]. To provide context to the measured element ratios, we compared them with a variety of space-relevant materials. We find an overlap with chondritic material for Mg/Si and Fe/Mg ratios. The observed range within the element ratios, however, indicates the contribution of a variety of minerals such as olivine, plagioclase or pyroxenes. Although our results agree with realistic mineral compositions, the calculated abundances of Al+ ions are still relatively uncertain and can be seen as an upper limit. Additionally, we present the results of a dynamical model, which allow us to derive the likely source region within the main rings of individually detected silicate grains. We find the C and B rings to be the most likely sources of the vast majority of grains with the D ring being only a minor source. Currently an analysis of compositional diversity between the different ring segments is under way. References [1] H.-W. Hsu et al. (2018) In situ collection of dust grains falling from Saturn’s rings into its atmosphere. Science 362. [2] N. Altobelli et al. (2016) Flux and composition of interstellar dust at Saturn from Cassini’s Cosmic Dust Analyzer. Science 352, 312–318. [3] R. Srama et al. (2004) The Cassini Cosmic Dust Analyzer. Space Science Reviews 114, 465–518. [4] K. Fiege et al. (2014) Calibration of relative sensitivity factors for impact ionization detectors with high-velocity silicate microparticles. Icarus 241, 336–345.

The gap between Saturn and its innermost D ring is populated with dust particles which primarily originate from the main rings. These particles were sampled by Cassini’s Cosmic Dust Analyzer (CDA) during the final mission phase, providing individual high-speed time-of-flight mass spectra. Compositionally, two main groups were observed, water ice and silicate particles. The relative frequencies of these spectral types vary with distance to Saturn’s ring plane (Hsu et al. 2018). In this study we present an approach to infer the composition of the silicate particles, which make up nearly 30% of the evaluated spectra, with the aim of deriving the elemental composition of minerals stemming from Saturn’s C and D rings. Owing to CDA’s relatively low mass resolution, spectral peaks from important mineral-forming ions such as Mg+, Al+ and Si+ are often unresolvable individually, forming a single broad peak. To remove this effect, we apply manual deconvolution, enabling the interferences to be disentangled and allowing the relative abundances of the different constituents to be measured. After combining the results of the deconvolution with experimentally-determined relative sensitivity factors (RSFs), converting ion abundances to elemental abundances (Fiege et al. 2014), we are able to infer elemental ratios within the particles and thus quantitatively measure their compositions. The grain detection locations allow C or D ring sources to be discriminated between, and this work represents the first in situ analysis of the rocky fraction in Saturn’s main rings, which until now was only accessible via remote sensing. Fiege, K., Trieloff, M., Hillier, J. K., Guglielmino, M., Postberg, F., Srama, R., Kempf, S., Blum, J.: Calibration of relative sensitivity factors for impact ionization detectors with high-velocity silicate microparticles, Icarus 241, 2014. Hsu, H.-W., Schmidt, J., Kempf, S., Postberg, F., Moragas-Klostermeyer, G., Seiß, M., Hoffmann, H., Burton, M., Ye, S.-Y., Kurth, W. S., Horányi, M., Khawaja, N., Spahn, F., Schirdewahn, D., O’Donoghue, J., Moore, L., Cuzzi, J., Jones, G. H., Srama, R.: In situ collection of dust grains falling from Saturn’s rings into its atmosphere, Science 362, 2018.

Different mass spectrometric approaches have been used to study the composition of ice and dust particles in space. Mass spectrometers onboard spacecraft such as Cassini, Rosetta and Giotto at Saturn, comet Churyumov-Gerasimenko and comet Halley respectively, have expanded our understanding of these planetary bodies by probing the composition of their dusty environments (Grün et al. 2019). The outstanding results from different space missions prove in situ mass spectrometry to be a reliable analytical tool with which to investigate the Solar System. Many of the mass spectrometers flown through the Solar System have used the impact ionisation technique, and an impact ionisation mass spectrometer, the Surface Dust Analyzer (SUDA), will be a part of NASA’s upcoming Europa-Clipper mission to Jupiter’s moon Europa. During the impact ionisation process, ice and dust grains impinging onto a detector’s solid target plate, at speeds above ≈ 1 km/s, generate a cloud of ions, neutrals and electrons (Srama et al. 2004; Auer & Sitte (1968)). The ions (cations in this work) are accelerated through a drift or reflectron region, towards a detector, from which time of flight mass spectra are generated (Friichtenicht et al. 1971).Electrostatic accelerators are used to calibrate (Mocker et al. 2012) impact ionization mass spectrometers on Earth, accelerating micron and submicron cosmic dust analogue grains, typically metallic or with a conductive coating, to suitable velocities. As the controlled acceleration of µm-sized ice grains to these hypervelocities is not yet possible in the laboratory, an analogue experiment using Laser Induced Liquid Beam Ion Desorption (LILBID), is employed to simulate the impact ionisation process of ice grains in space (Klenner et al. 2019). In the LILBID process, a thin stream of an aqueous solution of, for example, organic compounds is exposed to laser irradiation in a vacuum. The dissolved compounds, together with the solvent matrix, are ionized and fragment when the matrix, in which charges are stochastically distributed, is dispersed (e.g. Wiederschein et al. 2015). By varying the laser power, as well the ion collection efficiency, it is possible to simulate the spectra which result from impact ionisation at varying impact speeds (Wiederschein et al. 2015, Klenner et al. 2019). The resulting cation time of flight mass spectra then contain mass spectral features corresponding to organic fragments and water cluster species. This technique has been successfully used (Postberg et al. 2009, 2018; Khawaja et al. 2019) to simulate the mass spectra produced when Cassini’s Cosmic Dust Analyzer (CDA) sampled salt- and organic-bearing ice grains emitted into space by Saturn’s moon Enceladus.In this work we present a comparison between the mass spectral features of organic molecules generated by LILBID simulation of the impact ionisation mass spectra of organic-bearing ice grains, and the widely used standard technique of electron ionization (EI), the results of which can be found in existing databases, such as the National Institute of Standards and Technology (NIST) Chemistry WebBook. In electron-ionisation (EI), the sample is directly exposed to a beam of high-energy electrons (≈ 70 eV) which converts neutral molecules into molecular ions (M+) with high internal energies. Owing to the generated energies, the structures of the molecular ions become unstable and break up, producing a characteristic population of fragment ions. We have compared the cationic fragments of isomeric carbonyl compounds measured with LILBID and with those from EI obtained from the NIST WebBook database. The tested compounds are divided into three pairs of aldehydes and ketones i.e., propanal & acetone, butanal & 2-butanone, hexanal & 2-hexanone, with 3, 4 and 6 carbon atoms, respectively. To compare the spectral features related to organic fragments, water-cluster features are excluded from the LILBID spectra. In most cases, both the LILBID and EI spectra of the compounds show typical cleavage patterns characteristic of carbonyls.In ketones and aldehydes, for both LILBID and EI, we observe a correlation between the number of parent molecule carbon atoms and the relative intensities of particular cation fragments. We will present an in-depth comparison of the spectral features obtained from these techniques is currently, using LILBID spectra obtained for a mass spectral database applicable to the SUDA instrument on NASA’s Europa Clipper mission. The mass spectrometers (MASPEX & PEP-NIM) onboard Europa-Clipper, and ESA’s Jupiter Icy Moon Explorer (JUICE) spacecraft, respectively, will employ an EI (70 eV) technique, and the work presented here provides a valuable comparison and cross-calibration between the well-known EI and the more esoteric impact ionization techniques. Understanding the differences between the EI and impact-induced fragmentation and ionization behaviour of organics may also allow large existing libraries of EI spectra to be used to interpret the in situ impact ionization mass spectra of ice-free grains, such as those expected to be returned by JAXA’s Destiny+ mission to the unusual active asteroid 3200 Phaethon, progenitor of the Geminid meteor shower.ReferencesGrün, E., Krüger, H., & Srama, R. (2019) The dawn of dust astronomy, Space Sci Rev, 2015:46.Srama, R. et al. (2004). The Cassini cosmic dust analyzer. Space Sci Rev, 114(1– 4), 465–518.Auer, S., & Sitte, K., (1968). Detection technique for micrometeoroids using impact ionization. Earth and Planetary Sci Lett, 4,178–183Friichtenicht, J. F., Roy, N. L., & Moede, L. W. (1971). Cosmic Dust Analyzer. Technical Report NASA2CR2140241.Mocker, A. et al (2012). On the applicability of laser ionization for simulating hypervelocity impacts. Journal of Applied Physics, 112(10).Klenner, F. (2019), Analogue spectra for impact ionization mass spectra of water ice grains obtained at different impact speeds in space, Rapid Communications in Mass Spectrometry, 33(22), 1751–1760.Wiederschein, F. et al. (2015) Charge separation and isolation in strong water droplet impacts. Physical Chemistry Chemical Physics. PCCP, 17(10), 6858–64.Postberg, F. et al. (2009) Sodium salts in E ring ice grains from an ocean below the surface of Enceladus. Nature, 459, 1–4.Postberg, F. et al. (2018) Macromolecular organic compounds from the depths of Enceladus, Nature, 558(7711), pp. 564–568.Khawaja, N. et al. (2019) Low-mass nitrogen-, oxygen-bearing, and aromatic compounds in Enceladean ice grains, Monthly Notices of the Royal Astronomical Society, 489(4), pp. 5231–5243.

This study evaluates the dynamics of soil organic carbon (SOC) underperennial crops across the globe. It quantifies the effect of change fromannual to perennial crops and the subsequent temporal changes in SOCstocks during the perennial crop cycle. It also presents an empiricalmodel to estimate changes in the SOC content under crops as a functionof time, land use, and site characteristics. We used a harmonised globaldataset containing paired-comparison empirical values of SOC andincluding different types of perennial crops (perennial grasses, palms,and woody plants) with different end-uses: bioenergy, food, other bioproducts, and short rotation coppice crops. Salient outcomes include: a20-year period encompassing a change from annual to perennial cropsled to an average 20% increase in SOC at 0-30 cm (6.0 ± 4.6 Mg ha-1gain) and a total of 10% increase over the 0-100 cm soil profile (5.7 ±10.9 Mg ha-1). A change from natural pasture to perennial cropdecreased SOC stocks by 1% over 0-30 cm (-2.5 ± 4.2 Mg ha-1) and10% over 0-100 cm (-13.6 ± 8.9 Mg ha-1). The effect of a land usechange from forest to perennial crops did not have significant impacts,probably due to the limited number of plots; but the data indicated thatwhile a 2% increase in SOC was observed at 0-30 cm (16.81 ± 55.1 Mgha-1), a decrease of 24% was observed at 30-100 cm (-40.1 ± 16.8 Mgha-1); perennial crops generally accumulate SOC through time,especially woody crops; and temperature was the main driver explainingdifferences in SOC dynamics, followed by crop age, soil bulk density, claycontent and depth. We present empirical evidence showing that the FAOperennialization strategy is reasonable, underscoring the role ofperennial crops as a useful component of climate change mitigationstrategies.

The agricultural sector accounts for 70% of all water consumption and poses great pressure on ground water resources. Therefore, evaluating agricultural water consumption is highly important as it allows supply chain actors to identify practices which are associated with unsustainable water use, which risk depleting current water resources and impacting future production. However, these assessments are often not feasible for crop producers as data, models and experiments are required in order to conduct them. This work introduces a new on-line agricultural water use assessment tool that provides the water footprint and irrigation requirements at field scale based on an enhanced FAO56 approach combined with a global climate, crop and soil databases. This has been included in the Cool Farm Tool – an online tool which already provides metrics for greenhouse gas emissions and biodiversity impacts and therefore allows for a more holistic assessment of environmental sustainability in farming and agricultural supply chains. The model is tested against field scale and state level water footprint data providing good results. The tool provides a practical, reliable way to assess agricultural water use, and offers a means to engage growers and stakeholders in identifying efficient water management practices., Highlights • CFTW facilitates water use assessments in crop production in food supply chains. • Global on-line tool combining user input with a soil, daily climate and crop database. • Comparison to observed evapo-transpiration (R2 = 0.52) shows good agreement. • Comparison to observed total water footprint (R2 = 0.96) shows very good agreement. • Using CFTW can reduce errors in water footprints by >70% compared to state estimates.

In order to limit global warming to 2°C, a variety of mitigation measures are needed, including those that result in net negative emissions. Soil carbon sequestration (SCS) through changed land management practices has the potential to help meet this need, but it requires further study to represent a viable policy option. Rice cultivation plays a major role in South Asian agriculture, accounting for almost 40% of the crop’s harvested area worldwide. Its greenhouse gas (GHG) profile means it contributes disproportionately more than other crops to the region’s emissions. Adapting rice system management for SCS may therefore represent a compelling mitigation opportunity for the agricultural sectors of South Asian countries. This study uses a process-based modelling approach to compare the performance of two models, ECOSSE and DAYCENT, in assessing the mitigation potential of increasing soil organic carbon (SOC) stocks on a Bangladeshi test site under rice cultivation. A previous study using DAYCENT showed an increase in SOC stock as well as an overall GHG emissions reduction for several management practices relative to the baseline scenario. ECOSSE, calibrated to the same measurements, also showed an increase in SOC and net emissions reduction relative to the baseline. However, the models differed significantly in the extent of mitigation predicted as well as the GHG emissions profile. Given these differences, further analysis is needed to reduce error and uncertainty in these models. The results of this study form a basis for spatial model approaches to assess the mitigation potential of rice production in Bangladesh.

To limit warming to well below 2°C, most scenario projections rely on greenhouse gas removal technologies (GGRTs); one such GGRT uses soil carbon sequestration (SCS) in agricultural land. In addition to their role in mitigating climate change, SCS practices play a role in delivering agroecosystem resilience, climate change adaptability and food security. Environmental heterogeneity and differences in agricultural practices challenge the practical implementation of SCS, and our analysis addresses the associated knowledge gap. Previous assessments have focused on global potentials, but there is a need among policymakers to operationalise SCS. Here, we assess a range of practices already proposed to deliver SCS, and distil these into a subset of specific measures. We provide a multidisciplinary summary of the barriers and potential incentives towards practical implementation of these measures. First, we identify specific practices with potential for both a positive impact on SCS at farm level and an uptake rate compatible with global impact. These focus on: (a) optimising crop primary productivity (e.g. nutrient optimisation, pH management, irrigation); (b) reducing soil disturbance and managing soil physical properties (e.g. improved rotations, minimum till); (c) minimising deliberate removal of C or lateral transport via erosion processes (e.g. support measures, bare fallow reduction); (d) addition of C produced outside the system (e.g. organic manure amendments, biochar addition); (e) provision of additional C inputs within the cropping system (e.g. agroforestry, cover cropping). We then consider economic and non‐cost barriers and incentives for land managers implementing these measures, along with the potential externalised impacts of implementation. This offers a framework and reference point for holistic assessment of the impacts of SCS. Finally, we summarise and discuss the ability of extant scientific approaches to quantify the technical potential and externalities of SCS measures, and the barriers and incentives to their implementation in global agricultural systems., To limit warming to well below 2°C, many scenario projections rely on greenhouse gas removal by soil carbon sequestration (SCS) in agricultural land. Here, we provide a multidisciplinary summary of the barriers and potential incentives towards practical implementation SCS. First, we identify specific practices with potential for both a positive impact on SCS and an uptake rate compatible with global impact. Then, we then consider economic and non‐cost barriers and incentives for implementing SCS, and potential externalised impacts of implementation. Finally, we discuss the ability of existing methods to model the potential of SCS in global agricultural systems.

Updating and refining the N2O emission factors (N2O-EFs) are vital to reduce the uncertainty in estimates of direct N2O emissions. Based on a database with 1151 field measurements across China, the N2O-EFs were established via three approaches including the maximum likelihood method, a linear regression with an intercept and a linear regression with the intercept set to 0 using 70% of the observations. The remaining 30% of the observations were then used to evaluate the predicted N2O-EFs. The third method had the highest R2 of 0.39 and the best model efficiency of 0.38 with no significant bias, showing the best calculation efficiency. The results showed that the N2O-EFs varied with agroregions, crops, and management patterns. The agroregions of Huang-Huai-Hai and Yangtze River had the higher N2O-EFs in maize and wheat seasons than other regions, and the highest N2O-EFs of 0.66-0.92% in the rice season was found in the South and Southwest agroregions. Both fertilizer types and water regimes had the remarkable effects on N2O-EFs. Based on the best estimation by the selected method, direct N2O emissions from China's crop cultivation were estimated to be 194 Gg N2O-N with a 95% confidence interval of 180-208 Gg N2O-N in the year 2016.

Food production is estimated to emit between 20–30 % of global anthropogenic carbon emissions. The need to achieve net zero emissions requires a transition to low carbon, sustainable food sources. Of the total greenhouse gas (GHG) emissions for food production, only 4 % are attributed to wild capture fisheries. However, within seafood GHG studies a wide range of estimates can be found across different species, fishing methods and regions. This study assesses the environmental impact of fish capture, including the carbon footprint (CF), by the Scottish pelagic fleet, a highly modernised fleet targeting herring, mackerel and blue whiting in the North Sea and Atlantic Ocean. A life cycle assessment (LCA) was undertaken to provide a standardised comparison of pelagic fish with other seafood studies. One kg of whole round fish caught by the Scottish pelagic trawl fleet had a CF of 0.452 kg CO2 eq. Fuel burned during fishing operations was the largest contributing factor, accounting for approximately 96% of a CF. This figure was consistent with the expected results for a fishery for small pelagics, which are typically under 1 kg CO2 eq. per kg of whole fish landed. When contrasted with other seafood LCAs, the results were found to be lower than most other seafood. Our results demonstrate that Scottish-caught pelagic fish are a low carbon food source that could contribute to minimising food-related GHG emissions.

Agriculture is a major contributor to India's environmental footprint, particularly through greenhouse gas (GHG) emissions from livestock and fresh water used for irrigation. These impacts are likely to increase in future as agriculture attempts to keep pace with India's growing population and changing dietary preferences. Within India there is considerable dietary variation, and this study therefore aimed to quantify the GHG emissions and water usage associated with distinct dietary patterns. Five distinct diets were identified from the Indian Migration Study – a large adult population sample in India – using finite mixture modelling. These were defined as: Rice & low diversity, Rice & fruit, Wheat & pulses, Wheat, rice & oils, Rice & meat. The GHG emissions of each dietary pattern were quantified based on a Life Cycle Assessment (LCA) approach, and water use was quantified using Water Footprint (WF) data. Mixed-effects regression models quantified differences in the environmental impacts of the dietary patterns. There was substantial variability between diets: the rice-based patterns had higher associated GHG emissions and green WFs, but the wheat-based patterns had higher blue WFs. Regression modelling showed that the Rice & meat pattern had the highest environmental impacts overall, with 0.77 (95% CI 0.64–0.89) kg CO2e/capita/day (31%) higher emissions, 536 (95% CI 449–623) L/capita/day (24%) higher green WF and 109 (95% CI 85.9–133) L/capita/day (19%) higher blue WF than the reference Rice & low diversity pattern. Diets in India are likely to become more diverse with rising incomes, moving away from patterns such as the Rice & low diversity diet. Patterns such as the Rice & meat diet may become more common, and the environmental consequences of such changes could be substantial given the size of India's population. As global environmental stress increases, agricultural and nutrition policies must recognise the environmental impacts of potential future dietary changes., Graphical abstract Unlabelled Image, Highlights • India's food system produces large environmental impacts but these vary by diets. • We explored differences in GHG emissions and water use of Indian dietary patterns. • Rice-based diets had higher emissions but wheat-based diets used more water. • Diets with more animal products had the highest environmental impacts overall. • Diversifying diets in India may have severe consequences for environmental impacts.

CCAFS-MOT is a tool to support farmers, policy advisors and agricultural extension services on the choice of management practices that reduce greenhouse gas emissions (GHG) without risking food security. It is an Excel-based tool which brings together several empirical models to estimate GHG emissions in rice, cropland and livestock systems, and provides information about the most effective mitigation options. Greenhouse gas emissions are estimated in terms of carbon dioxide equivalent per hectare (kg CO2eq ha− 1) and carbon dioxide equivalent per unit of product (kg CO2eq kg− 1). Baseline management practices are chosen by the user and a set of mitigation options are ranked according to their mitigation potential. The tool allows different levels of input to be specified from an introductory to detailed level, depending on objectives and issues like to accommodate users with different backgrounds and details concerning input data. As such it allows for product and region specific assessments of GHGs and mitigation potentials to be made without the need for expert knowledge or for lengthy model set-up and calibration.

There has been much debate about the uncertainties associated with the estimation of direct and indirect agricultural nitrous oxide (N2O) emissions in developing countries and in particular from tropical regions. In this study, we report an up-to-date review of the information published in peer-review journals on direct N2O emissions from agricultural systems in tropical and sub-tropical regions. We statistically analyze net-N2O-N emissions to estimate tropic-specific annual N2O emission factors (N2O-EFs) using a Generalized Additive Mixed Model (GAMM) which allowed the effects of multiple covariates to be modelled as linear or smooth non-linear continuous functions. Overall the mean N2O-EF was 1.2% for the tropics and sub-tropics, thus within the uncertainty range of IPCC-EF. On a regional basis, mean N2O-EFs were 1.4% for Africa, 1.1%, for Asia, 0.9% for Australia and 1.3% for Central & South America. Our annual N2O-EFs, estimated for a range of fertiliser rates using the available data, do not support recent studies hypothesising non-linear increase N2O-EFs as a function of applied N. Our findings highlight that in reporting annual N2O emissions and estimating N2O-EFs, particular attention should be paid in modelling the effect of study length on response of N2O.

Highlights • Highest GHG emissions from food production are from rice and ruminant products. • Highest GHG emissions from consumption are from rice and livestock products. • Consumption choice can either increase or decrease total GHG emissions., Agriculture is a major source of greenhouse gas (GHG) emissions globally. The growing global population is putting pressure on agricultural production systems that aim to secure food production while minimising GHG emissions. In this study, the GHG emissions associated with the production of major food commodities in India are calculated using the Cool Farm Tool. GHG emissions, based on farm management for major crops (including cereals like wheat and rice, pulses, potatoes, fruits and vegetables) and livestock-based products (milk, eggs, chicken and mutton meat), are quantified and compared. Livestock and rice production were found to be the main sources of GHG emissions in Indian agriculture with a country average of 5.65 kg CO2eq kg−1 rice, 45.54 kg CO2eq kg−1 mutton meat and 2.4 kg CO2eq kg−1 milk. Production of cereals (except rice), fruits and vegetables in India emits comparatively less GHGs with

The world population is projected to increase to 9–10 billion by 2050, during which time it will be necessary to reduce anthropogenic greenhouse gas emissions to mitigate climate change. The particular challenge this places on agriculture is to identify practices which ensure stable and productive food supply that also have a low greenhouse gas (GHG) intensity. Maize is the principle staple crop in many parts of Africa with low and variable yields, averaging only 1.6 t/ha in sub-Saharan Africa (SSA). Food security and increasing crop yields are considered priorities in SSA over impacts of food production on GHG emissions. Here we describe an approach that can be used to inform a decision support tree for optimal interventions to obtain sufficient food production with low GHG intensity, and we demonstrate its applicability to SSA. We employed a derivative of the farm greenhouse gas calculator ‘Cool Farm Tool’ (CFT) on a large survey of Kenyan and Ethiopian smallholder maize-based systems in an assessment of GHG intensity. It was observed that GHG emissions are strongly correlated with nitrogen (N) input. Based on the relationship between yield and GHG emissions established in this study, a yield of 0.7 t/ha incurs the same emissions as those incurred for maize from newly exploited land for maize in the region. Thus, yields of at least 0.7 t/ha should be ensured to achieve GHG intensities lower than those for exploiting new land for production. Depending on family size, the maize yield required to support the average consumption of maize per household in these regions was determined to be between 0.3 and 2.0 t/ha, so that the desirable yield can be even higher from a food security perspective. Based on the response of the observed yield to increasing N application levels, average optimum N input levels were determined as 60 and 120 kg N/ha for Kenya and Ethiopia, respectively. Nitrogen balance calculations could be applied to other countries or scaled down to districts to quantify the trade-offs, and to optimise crop productivity and GHG emissions.

Increasing concerns about global environmental change and food security have focused attention on the need for environmentally sustainable agriculture. This is agriculture that makes efficient use of natural resources and does not degrade the environmental systems that underpin it, or deplete natural capital stocks. We convened a group of 29 ‘practitioners' and 17 environmental scientists with direct involvement or expertise in the environmental sustainability of agriculture. The practitioners included representatives from UK industry, non-government organizations and government agencies. We collaboratively developed a long list of 264 knowledge needs to help enhance the environmental sustainability of agriculture within the UK or for the UK market. We refined and selected the most important knowledge needs through a three-stage process of voting, discussion and scoring. Scientists and practitioners identified similar priorities. We present the 26 highest priority knowledge needs. Many of them demand integration of knowledge from different disciplines to inform policy and practice. The top five are about sustainability of livestock feed, trade-offs between ecosystem services at farm or landscape scale, phosphorus recycling and metrics to measure sustainability. The outcomes will be used to guide ongoing knowledge exchange work, future science policy and funding.

Systems approaches have great potential for application in predictive ecology. In this paper, we present a range of examples, where systems approaches are being developed and applied at a range of scales in the field of global change and biogeochemical cycling. Systems approaches range from Bayesian calibration techniques at plot scale, through data assimilation methods at regional to continental scales, to multi-disciplinary numerical model applications at country to global scales. We provide examples from a range of studies and show how these approaches are being used to address current topics in global change and biogeochemical research, such as the interaction between carbon and nitrogen cycles, terrestrial carbon feedbacks to climate change and the attribution of observed global changes to various drivers of change. We examine how transferable the methods and techniques might be to other areas of ecosystem science and ecology.

In order to predict the response of carbon (C)-rich soils to external change, models are needed that accurately reflect the conditions of these soils. Here we present an example application of the new Estimation of Carbon in Organic Soils - Sequestration and Emissions (ECOSSE) model to estimate net change in soil C in response to changes in land use in Scotland. The ECOSSE estimate of annual change in soil C stocks for Scotland between 2000 and 2009 is -810 ± 89 kt yr -1 , equivalent to 0.037 ± 0.004% yr -1 . Increasing the area of land-use change from arable to grass has the greatest potential to sequester soil C, and reducing the area of change from grass to arable has the greatest potential to reduce losses of soil C. Across Scotland, simulated changes in soil C from C-rich soils (C content >6%) between 1950 and 2009 is -63 Mt, compared with -35 Mt from non-C-rich mineral soils; losses from C-rich soils between 2000 and 2009 make up 64% of the total soil C losses. One mitigation option that could be used in upland soils to achieve zero net loss of C from Scottish soils is to stop conversion of semi-natural land to grassland and increase conversion of grassland to semi- natural land by 125% relative to the present rate. Mitigation options involving forestry are not included here because the data available to calculate losses of soil C do not account for losses of soil C on drainage of semi-natural land.