A few months after NASA's decision in November 2018 that Jezero Crater would be the landing site for the Mars 2020 rover mission, the research article The Geology and Astrobiology of McLaughlin Crater, Mars: An Ancient Lacustrine Basin Containing Turbidites, Mudstones, and Serpentinites was published.
McLaughlin is a 92 km diameter complex crater that formed ~4 billion years ago and contained a large and deep Martian lake circa 3.8 Ga, so 200-200 million years older than the lake that once existed in Jezero.
Some keypoints in the article:
- The lake has features unlike any other known Martian paleolakes
- Sedimentary units include delta deposits, turbidites, and deep-water sediments; and hydrothermal deposits include serpentinites
- Geochemical gradients occured in a long-lived lake that was in sustained communication with groundwater and subsurface environments
Two of the authors also participated in a workshop for human missions to the surface of Mars a few years earlier with the article McLAUGHLIN CRATER AS A CANDIDATE LANDING SITE FOR HUMANS ON MARS., in which they argue that the crater also contains volatile-rich rocks that will be high quality, accessible targets for ISRU and that it provides a flat, low-risk and low-elevation landing zone, which will facilitate landing large payloads on Mars.
Alternatively, there are the landing sites with subsurface water ice and low scientific value.
From NASA's Treasure Map for Water Ice on Mars:
Water ice will be a key consideration for any potential landing site. With little room to spare aboard a spacecraft, any human missions to Mars will have to harvest what's already available for drinking water and making rocket fuel.
But with the first mission the spacecraft has to carry then all the equipment to make that drinking water and rocket fuel and to mine that ice. And isn't it a great risk to rely fully on that equipment to survive for the first time ?
