Mapping Lava Flows on Venus Using SAR and InSAR: Hawaiʻi Case Study.

We explore the potential for repeat‐pass SAR Interferometry (InSAR) correlation to track volcanic activity on Venus' surface motivated by future SAR missions to Earth's sister planet. We use Hawai'i as a natural laboratory to test whether InSAR can detect lava flows assuming orbital and instrument parameters similar to that of a Venus mission. Hawai'i was chosen because lava flows are frequent, and well documented by the United States Geological Survey, and because Hawai'i is a SAR supersite, where space agencies have offered open radar data sets for analysis. These data sets have different wavelengths (L, C, and X bands), bandwidths, polarizations, look angles, and a variety of orbital baselines, giving opportunity to assess the suitability of parameters for detecting lava flows. We analyze data from ALOS‐2 (L‐band), Sentinel‐1 (C‐band), and COSMO‐SkyMed (X‐band) spanning 2018 and 2022. We perform SAR amplitude and InSAR correlation analysis over temporal baselines and perpendicular baselines similar to those of a Venus mission. Fresh lava flows create a sharp, noticeable decrease in InSAR correlation that persists indefinitely for images spanning the event. The same lava flows are not always visible in the corresponding amplitude images. Moreover, noticeable decorrelation persists in image pairs acquired months after the events due to post‐emplacement contraction of flows. Post‐emplacement effects are hypothesized to last longer on the Venusian surface, increasing the likelihood of detecting Venus lava flows using InSAR. We argue for further focus on repeat‐pass InSAR capabilities in upcoming Venus missions, to detect and quantify volcanic activity on Earth's hotter twin. Plain Language Summary: Scientists are still unsure whether volcanic activity is presently occurring on Venus. Future missions to Venus may have the opportunity to detect new lava flows on Venus' surface using a process called interferometry, in which two radar images of a planet's surface over time are compared to see what's changed between them. Interferometry has been used to detect lava and volcanic activity on Earth in the past. We use Hawai'i as a natural laboratory, measuring lava flows there with interferometry, under simulated conditions of a Venus mission, to test whether it will be possible for future Venus missions to track lava flows with interferometry. From the results of our case study, we believe that future missions to Venus such as NASA's VERITAS will be able to do exactly that. Key Points: Under favorable mission and instrument conditions, SAR Interferometry (InSAR) can detect lava flows on VenusInSAR correlation effects from thermal subsidence can be seen for several months post‐lava‐flow‐emplacementLava flows are more easily visible in InSAR correlation maps than in differenced SAR amplitude maps [ABSTRACT FROM AUTHOR]