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Longitudinal structures in the Martian thermosphere and topside ionosphere between 150 and 200 km altitudes are studied using in situ electron and neutral measurements from the NASA Mars Atmosphere and Volatile EvolutioN (MAVEN) mission. Four time intervals are selected for comparison, during which MAVEN sampled similar local time (9.3-10.3 h) and latitude (near 20°S) regions but at different solar longitude positions (two near northern summer solstice, one each at northern vernal and autumnal equinoxes). Persistent and pronounced tidal oscillations characterize the ionosphere and thermosphere, whose longitudinal variations in density are generally in-phase with each other. Our analysis of simultaneous and collocated neutral and electron data provides direct observational evidence for thermosphere-ionosphere coupling through atmospheric tides. We conclude that the ionosphere is subject to modulation by upward-propagating thermal tides, via both tide-induced vertical displacement and photochemical reactions. Atmospheric tides constitute a ubiquitous and significant perturbation source to the ionospheric electron density, up to ~15% near 200 km.

In order to further evaluate the behavior of ionospheric variations at Mars, we investigate the Martian ionosphere-thermosphere (IT) perturbations associated with non-migrating thermal tides using over four years of Mars Atmosphere and Volatile Evolution (MAVEN) in situ measurements of the IT electron and neutral densities. The results are consistent with those of previous studies, namely strong correlation between the tidal perturbations in electron and neutral densities on the dayside at altitudes ~150-185 km, as expected from photochemical theory. In addition, there are intervals during which this correlation extends to higher altitudes, up to ~270 km, where diffusive transport of plasma plays a dominant role over photochemical processes. This is significant because at these altitudes the thermosphere and ionosphere are only weakly coupled through collisions. The identified non-migrating tidal wave variations in the neutral thermosphere are predominantly wave-1, wave-2, and wave-3. Wave-1 is often the dominant wavenumber for electron density tidal variations, particularly at high altitudes over crustal fields. The Mars Climate Database (MCD) neutral densities (below 300 km along the MAVEN orbit) shows clear tidal variations which are predominantly wave-2 and wave-3, and have similar wave amplitudes to those observed., Competing Interests: Conflicts of Interest: The authors declare no conflicts of interest.

The thermosphere of Mars is the interface through which the planet is continuously losing its reservoir of atmospheric volatiles to space. The structure and dynamics of the thermosphere is driven by a global circulation that redistributes the incident energy from the Sun. We report mapping of the global circulation in the thermosphere of Mars with the Mars Atmosphere and Volatile Evolution (MAVEN) spacecraft. The measured neutral winds reveal circulation patterns simpler than those of Earth that persist over changing seasons. The winds exhibit pronounced correlation with the underlying topography owing to orographic gravity waves., (Copyright © 2019 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.)

Many autistic individuals are less fit and have more health problems than their nonautistic peers. These findings suggest a need to develop effective physical activity interventions. Motor skill deficits, lack of motivation, and limited opportunities for physical activity may restrict exercise participation. Peer mentors can help autistic college students increase their physical activity level and fitness. We developed a 10-week peer mentored physical activity program that affords autistic college students the opportunity to act in a self-determined manner in which students are encouraged to engage in preferred activities and self-directed instruction (autonomy), gain skills through access to expert instruction (competence), and engage socially with peers (relatedness). The ability to act with self-determination may increase students' motivation to participate in physical activity. From our pilot study, we learned that autistic college students could improve their cardiorespiratory fitness, flexibility, and upper body muscular endurance as a result of participating in Into Fitness Together. We also learned of three shared themes: students felt that they gained motor competence, improved their health, and felt a sense of belonging. The autistic students spent time with both autistic and nonautistic peers, which fostered this belongingness. Access to movement experts and peer mentors in an individualized program that affords choice in physical activity is a step in the right direction to eliminate the health disparities of autistic young adults., Lay Summary: Why was this program developed?We developed a physical activity program because we saw the need for autistic individuals to benefit from regular physical activity. Motor skill challenges may keep autistic adults from engaging in regular physical activity and from reaping the benefits of improved fitness. Since participating in regular physical activity is important for the health of all individuals, it is important to design programs that address barriers so all people can benefit.What new program was developed?We developed a 10-week physical activity program called I nto Fi tness T ogether (IFiT) for autistic college students. The program is unique because it is individualized, tailored to autistic adults, fun, and has a built-in one-to-one peer support system.What did the researchers do?We wanted to learn whether the program had the potential to increase health-related fitness and how autistic college students experienced IFiT. Sixteen autistic college students participated in IFiT. They were paired one-on-one with another college student (known as a peer mentor) who was an expert in exercise science. The pairs worked out together 2.5 hours a week for 10 consecutive weeks. We examined change in participants' fitness levels at the start and end of IFiT. We also interviewed the autistic peers to understand their IFiT experience.What was the result of participating in the program?With regular participation in physical activity, the autistic peers improved their cardiorespiratory fitness levels, muscular endurance, and flexibility by the end of IFiT. There were three main themes that emerged from the interviews. At the end of the program, participants reported (1) greater competence in motor skills and a greater understanding of exercise, (2) improved overall health, and (3) a sense of belonging. Participants said they learned new ways to exercise, how to exercise correctly, and stated that they felt healthy and fit. They also expressed a sense of belonging. Participants stated that they valued their time with their peer mentor not only because the peer mentor shared their expertise in physical activity and exercise, but also because the peers talked about school, hobbies, and life in general. Having ongoing opportunities for regular social interaction was a positive experience for IFiT participants.What are the next steps for program development?This emerging practice article describes a small pilot study performed at one university, thus results cannot be generalized. Also, we did not have data from a comparison group of autistic students who did not participate in the program. Future studies should use a control and comparison group and gather data at multiple institutions.How will these findings help autistic adults now or in the future?There is limited information on interventions focused on physical activity for autistic college students; therefore, our work provides insight into a promising program. Regular physical activity can lead to positive health outcomes, skill acquisation, and participating in IFiT can potentially set the stage for lifelong physical activity., Competing Interests: No competing financial interests exist., (Copyright 2019, Mary Ann Liebert, Inc., publishers.)

We report the first global, time-dependent simulation of the Mars upper atmospheric responses to a realistic solar flare event, an X8.2 eruption on 10 September 2017. The Mars Global Ionosphere-Thermosphere Model runs with realistically specified flare irradiance, giving results in reasonably good agreement with the Mars Atmosphere and Volatile EvolutioN spacecraft measurements. It is found that the ionized and neutral regimes of the upper atmosphere are significantly disturbed by the flare but react differently. The ionospheric electron density enhancement is concentrated below ~110-km altitude due to enhanced solar X-rays, closely following the time evolution of the flare. The neutral atmospheric perturbation increases with altitude and is important above ~150-km altitude, in association with atmospheric upwelling driven by solar extreme ultraviolet heating. It takes ~2.5 hr past the flare peak to reach the maximum disturbance and then additional ~10 hr to generally settle down to preflare levels.

The Mars Atmosphere and Volatile EvolutioN (MAVEN) Neutral Gas and Ion Mass Spectrometer (NGIMS) provides sensitive detections of neutral gas and ambient ion composition. NGIMS measurements of nine atomic and molecular neutral species, and their variation with altitude, latitude, and solar zenith angle are reported over several months of operation of the MAVEN mission. Sampling NGIMS signals from multiple neutral species every several seconds reveals persistent and unexpectedly large amplitude density structures. The scale height temperatures are mapped over the course of the first few months of the mission from high down to midlatitudes. NGIMS measurements near the homopause of 40 Ar/N 2 ratios agree with those reported by the Sample Analysis at Mars investigation and allow the altitude of the homopause for the most abundant gases to be established.

The Mars Atmosphere and Volatile Evolution (MAVEN) mission, during the second of its Deep Dip campaigns, made comprehensive measurements of martian thermosphere and ionosphere composition, structure, and variability at altitudes down to ~130 kilometers in the subsolar region. This altitude range contains the diffusively separated upper atmosphere just above the well-mixed atmosphere, the layer of peak extreme ultraviolet heating and primary reservoir for atmospheric escape. In situ measurements of the upper atmosphere reveal previously unmeasured populations of neutral and charged particles, the homopause altitude at approximately 130 kilometers, and an unexpected level of variability both on an orbit-to-orbit basis and within individual orbits. These observations help constrain volatile escape processes controlled by thermosphere and ionosphere structure and variability., (Copyright © 2015, American Association for the Advancement of Science.)

Coupling between the lower and upper atmosphere, combined with loss of gas from the upper atmosphere to space, likely contributed to the thin, cold, dry atmosphere of modern Mars. To help understand ongoing ion loss to space, the Mars Atmosphere and Volatile Evolution (MAVEN) spacecraft made comprehensive measurements of the Mars upper atmosphere, ionosphere, and interactions with the Sun and solar wind during an interplanetary coronal mass ejection impact in March 2015. Responses include changes in the bow shock and magnetosheath, formation of widespread diffuse aurora, and enhancement of pick-up ions. Observations and models both show an enhancement in escape rate of ions to space during the event. Ion loss during solar events early in Mars history may have been a major contributor to the long-term evolution of the Mars atmosphere., (Copyright © 2015, American Association for the Advancement of Science.)

The Mars Global Surveyor (MGS) z-axis accelerometer has obtained over 200 vertical structures of thermospheric density, temperature, and pressure, ranging from 110 to 170 kilometers, compared to only three previous such vertical structures. In November 1997, a regional dust storm in the Southern Hemisphere triggered an unexpectedly large thermospheric response at mid-northern latitudes, increasing the altitude of thermospheric pressure surfaces there by as much as 8 kilometers and indicating a strong global thermospheric response to a regional dust storm. Throughout the MGS mission, thermospheric density bulges have been detected on opposite sides of the planet near 90 degreesE and 90 degreesW, in the vicinity of maximum terrain heights. This wave 2 pattern may be caused by topographically-forced planetary waves propagating up from the lower atmosphere.