Publications

Abstract Distinguishing planetary formation and evolution pathways and understanding the origins of volatiles on planetary bodies requires determination of relative abundances and isotope ratios in the noble gases, and also of the isotope ratios in C, H, N, O and S at high precisions. Traditional planetary mass spectrometers uniquely provide excellent survey capability including the noble gas relative abundances and their isotope ratios. However, to distinguish planetary evolution models for the outer planets, stable isotope ratios in C and O require precisions of ∼10‰ or better, readily achievable with a tunable laser spectrometer (TLS). As demonstrated on the Mars Curiosity rover, and as planned for a now-selected NASA Venus mission, tunable laser spectrometers play a unique role synergistic with the capabilities of planetary mass spectrometers. The TLS technique of recording infrared absorption spectra at ultrahigh resolution (resolving power $\lambda $ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>λ</mml:mi></mml:math> / $\delta \lambda \sim 5$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>δ</mml:mi><mml:mi>λ</mml:mi><mml:mo>∼</mml:mo><mml:mn>5</mml:mn></mml:math> million) provides unambiguous detection of a wide variety of gases such as H 2 O, H 2 O 2 , H 2 CO, HOCl, NO, NO 2 , HNO 3 , N 2 O, O 3 , CO, CO 2 , NH 3 , N 2 H 4 , PH 3 , H 2 S, SO 2 , OCS, HCl, HF, O 2 , HCN, and CH 4 , C 2 H 2 , C 2 H 4 , C 2 H 6 at parts-per-billion levels. Through line-depth or line-area ratio comparisons of adjacent spectral lines, planetary TLS instruments can achieve isotope ratio measurements in C, H, N, O, and S molecules at precisions of ∼1–2‰, including for the triple isotope components of O and S. Expected performance of TLS instruments for Venus, Saturn, Enceladus and Uranus will be described as constrained by actual measurements reported at Mars on the Curiosity rover.

Abstract Geologic and climatic processes on modern‐day Mars are heavily influenced by aeolian surface activity, yet the relationship between atmospheric conditions and sediment mobilization is not well understood. The Interior Exploration using Seismic Investigations, Geodesy, and Heat Transport (InSight) spacecraft is uniquely able to address this issue, due to its joint imaging and continuous high‐frequency meteorological capabilities, which allow for direct comparison between surface activity and atmospheric conditions. Since landing in the volcanic plains of Elysium Planitia, InSight's camera's have recorded intermittent, small‐scale surface changes, including removal of fine material on the lander footpad, linear tracks and localized surface darkening caused by minor dust removal, and surface creep of granules, as presented in Part 1 (Charalambous et al., 2021, this issue). Surface activity is found to correlate well with the timing of abrupt pressure drops (Δ P ∼ 1–9 Pa) and transient wind gusts ( v ∼ 14–31 m/s) associated with convective vortex passage. Here we identify the major erosive forces acting on surface particles during these events, including the vertical pressure gradient force at the vortex core and the drag force generated by quickly‐rotating tangential winds. Orbital and ground‐truth data suggest that aeolian activity at InSight's landing site is sporadic under modern climatic conditions. Ongoing aeolian surface modifcation is driven primarily by turbulent vortices that sporadically lift dust and redistribute coarser sediment (i.e., sand and granules) but do not aid in the development of organized aeolian bedforms. Surface erosion is localized within the path these vortices take across the surface which is controlled by seasonally‐reversing background circulation patterns.

I. Mitrofanov, W. Boynton, G. Chin, D. Golovin, L. Evans, K. Harshman, J. Garvin, A. Kozyrev, M. Litvak, T. McClanahan, A. Malakhov, G. Milikh, M. Mokrousov, G. Nandikotkur, I. Nuzhdin, A. Sanin, R. Starr, R.Sagdeev, V. Shevchenko, V. Shvetsov, V. Tretyakov, J. Trombka, A. Varennikov and A. Vostrukhin, Institute for Space Research of Russian Academy of Science, 117997 Moscow, Russia, mitrofanov@l503.iki.rssi.ru; University of Arizona, Tucson, USA; NASA Goddard Space Flight Center, Greenbelt, USA; Computer Science Corporation, Greenbelt, USA; University of Maryland, College Park, USA; Catholic University, Washington DC, USA; Sternberg Astronomical Institute of Moscow State University, Moscow, Russia; Joint Institute of Nuclear Energy, Dubna, Moscow

Abstract Europa is a premier target for advancing both planetary science and astrobiology, as well as for opening a new window into the burgeoning field of comparative oceanography. The potentially habitable subsurface ocean of Europa may harbor life, and the globally young and comparatively thin ice shell of Europa may contain biosignatures that are readily accessible to a surface lander. Europa’s icy shell also offers the opportunity to study tectonics and geologic cycles across a range of mechanisms and compositions. Here we detail the goals and mission architecture of the Europa Lander mission concept, as developed from 2015 through 2020. The science was developed by the 2016 Europa Lander Science Definition Team (SDT), and the mission architecture was developed by the preproject engineering team, in close collaboration with the SDT. In 2017 and 2018, the mission concept passed its mission concept review and delta-mission concept review, respectively. Since that time, the preproject has been advancing the technologies, and developing the hardware and software, needed to retire risks associated with technology, science, cost, and schedule.