The WISDOM Radar: Unveiling the Subsurface Beneath the ExoMars Rover and Identifying the Best Locations for Drilling

Abstract

The search for evidence of past or present life on Mars is the principal objective of the 2020 ESA-Roscosmos ExoMars Rover mission. If such evidence is to be found anywhere, it will most likely be in the subsurface, where organic molecules are shielded from the destructive effects of ionizing radiation and atmospheric oxidants. For this reason, the ExoMars Rover mission has been optimized to investigate the subsurface to identify, understand, and sample those locations where conditions for the preservation of evidence of past life are most likely to be found. The Water Ice Subsurface Deposit Observation on Mars (WISDOM) ground-penetrating radar has been designed to provide information about the nature of the shallow subsurface over depth ranging from 3 to 10 m (with a vertical resolution of up to 3 cm), depending on the dielectric properties of the regolith. This depth range is critical to understanding the geologic evolution stratigraphy and distribution and state of subsurface H2O, which provide important clues in the search for life and the identification of optimal drilling sites for investigation and sampling by the Rover's 2-m drill. WISDOM will help ensure the safety and success of drilling operations by identification of potential hazards that might interfere with retrieval of subsurface samples. Key Words: Ground penetrating radar—Martian shallow subsurface—ExoMars. Astrobiology 17, 565–584.

Contemporary Liquid Brine Exploration on Mars: From Spectral Unmixing to Subpixel Mapping

“…Of course, attempts have been made to confirm the source of the liquid water (Carr et al, 2017), and sampling locations on Mars have included subsurface regions (Byrne et al, 2009;Dundas et al, 2014;Jones et al, 2011). These subsurface regions can be accessed by drilling or via geological features such as lava tubes, within which the search for Extra-Terrestrial Genomes can be used to target extant or recently dead life (Ciarletti et al, 2017), given the limited lifetime of DNA on Earth (~106 years, due to hydrolysis) and on Mars (~107 years, due to self-radiation) under otherwise protected conditions (Carr et al, 2016;Hays et al, 2017).…”

The PanCam Instrument for the ExoMars Rover

“…Determination of the subsurface stratigraphic extent of candidate sampling strata through combining PanCam DTMs of rock outcrops with WISDOM data (Ciarletti et al, 2017 , in this issue) will also be a key input into deciding where to drill. The three landing sites are all hypothesized to contain fine-grained sedimentary rocks.…”

“…From these data, an outcrop target will be chosen for the rover to approach to ∼3 m on the second sol. ADRON (Mitrofanov et al, 2017 , in this issue) and WISDOM (Ciarletti et al, 2017 , in this issue) surveys are conducted during the approach phase. A WAC image using either all 12 geology filters or selected groups (as discussed in Section 3.1 ) is taken of the outcrop along with a mosaic of eight HRC color images (and again eight co-registered ISEM spectra).…”

“…In addition, the Close-UP Imager (CLUPI; Josset et al, 2017 , in this issue) will provide high-resolution images of potential drilling sites and other interesting samples. Subsurface context will be provided by a ground-penetrating radar (Water Ice and Subsurface Deposit Observation On Mars, WISDOM; Ciarletti et al, 2017 , in this issue) and a neutron detector (Autonomous Detector of Radiation Of Neutrons, ADRON; Mitrofanov et al 2017 , in this issue), as well as a visible-IR spectrometer (Mars Multispectral Imager for Subsurface Studies, Ma_MISS; De Sanctis et al, 2017 , in this issue) in the drill tip to provide in situ mineralogy for the subsurface samples before they are brought to the surface. Sample analysis will be by the Analytical Laboratory Drawer (ALD) instruments, MicrOmega (Bibring et al, 2017 , in this issue), RLS (Raman spectrometer; Rull et al, 2017 , in this issue), and Mars Organic Molecule Analyser (MOMA; Goesmann et al, 2017 , in this issue).…”

Probing groundwater in arid environments: challenges and opportunities south of the Mediterranean basin

“…With the exception of Mars' icy polar-layered deposits, the ability of sounding radar to detect liquid water (e.g., Orosei et al 2018) in desiccated and rocky terrains has been compromised by the high electrical conductivity that constitutes Mars' volcanic upper crust (Heggy et al 2006). Additional shallow subsurface radar investigations include two ground penetrating radar experiments for Mars aboard NASA's Mars 2020 rover and ESA's ExoMars rover (Ciarletti et al 2017); SELENE radar for the Moon (Ono et al 2008); CONSERT radar for comet 67P (Kofman et al 2015); and two sounding radars aboard the JUICE (ESA) and Europa Clipper (NASA) missions exploring the Jovian icy moons (Heggy et al 2017); and are all examples of how radar probing techniques have taken the search for subsurface volatiles on planetary surfaces from a local scale to a global one.…”