Every NASA landed Mars mission – except the 1996 Pathfinder mission that focused on technology demonstration – has had the goal of exploring Mars’ past and current potential for life or pre-biotic chemistry. For the MER rovers, the goal was simply to determine whether water – an essential ingredient for life – was present at the surface early in Mars’ history. The Curiosity rover is exploring Gale Crater to examine soils from many eras of Martian history to determine whether or not environments for life existed and to determine whether biosignatures of past life remain. The 2018 ExoMars rover will explore another site on Mars for its astrobiology potential.

The SDT has proposed that the 2020 rover continue the strategy and pursue astrobiology as the mission’s defining goal. Its proposed strategy breaks into two parts. The first is to have the rover carry a suite of instruments capable of a exploring site’s geologic history in-depth with an emphasis on how that history affected the possible presence of past life.

The team proposes that the rover carry multispectral cameras for obtaining images and an imaging spectrometer for analyzing composition across entire sites. These instruments would provide the context to interpreting each locale’s history as well as allowing the science team to select specific targets for more detailed exploration.

For most of the contact science, the SDT is proposing that the rover carry a new generation of instruments. Current Mars rover contact spectrometers measure mean composition over an approximately two centimeter contact area. The new generation of instruments under development can make composition measurements for spots as small as a tenth of a millimeter. With that resolution, the contact spectrometers would make dozens to hundreds of measurements across the contact area.

If you take a close look at soils and most rocks, you’ll see that most are composites of many fragments that each have their own geological story to tell. The contact spectrometers that are likely to be proposed for the 2020 rover will be capable of exploring each of those fragments individually. (The SDT also proposes that the rover carry an imaging microscope to study the morphology and texture of each contact area.)

The remote sensing and contact instruments listed above are included in the baseline recommendations and are expected to be affordable at the low end of the expected budget (~$90M to $125M) for the science instruments. If the budget becomes plusher, the SDT recommends two additional instruments to study the shallow subsurface beneath the rover. A ground penetrating radar would detect subsurface rock and soil layers, providing better context for understanding the geology exposed at the surface. A gamma ray spectrometer would measure the composition of soil in the upper few centimeters and could alert scientists to interesting substances just below the upper veneer of soil.

A capable instrument suite enables scientific exploration; the rover still must be delivered to a location that orbital instruments show might have been a location for life or pre-biotic chemistry. A number of such locations are known, and more are being searched for. However, these sites often lie within rough terrains with just a small area free of large rocks that would end the mission should the rover be unlucky enough to land on one. The 2020 rover mission will inherit the precision landing system developed for the Curiosity rover that reduced the area of the landing ellipse to a fraction of what it had been for previous landers.

The SDT recommends shrinking that ellipse further to allow more landing sites to be considered. On past missions, the parachute has opened at the earliest possible time during the descent. For the 2020 descent, the SDT recommends that the entry system have the ability to vary the time of opening based on its estimate of its position relative to the landing zone. This relatively simple enhancement could reduce the size of the landing ellipse by 25% to 50%.

Many potentially interesting astrobiology sites on Mars lack any area the size of a landing ellipse free of large rocks or dangerously steep slopes. A second enhancement the SDT asked NASA to consider is terrain recognition navigation (TRN) that would enable the lander to compare images of the landing area stored on board with real-time images taken during the descent. This capability would allow the descent system to determine its actual location and steer free of hazardous terrain in the moments of final descent.

Goal B: “Assess the biosignature preservation potential within the selected geological environment and search for potential biosignatures.”