Both NASA and ESA hope their next Mars rovers will find evidence that life once thrived on Mars, but they have different strategies to reach this goal. Their landing site choices reflect this difference.
Engineers are assembling two ambitious rover missions for launch in 2020. Both seek to drill into Mars’s ancient sedimentary rocks in the hopes of finding evidence that life once thrived there.
But they have contrasting approaches to analysing the drilled samples. ESA’s ExoMars rover (recently named after DNA pioneer Rosalind Franklin) plans to study them in situ; NASA’s Mars 2020 rover will collect and document a set of samples for later return to Earth.
Both missions seek to understand the environmental conditions that prevailed when Mars was young, only about half a billion years after planetary formation. At the time, the atmospheres of both planets were dominated by carbon dioxide, and both enjoyed fluvial activity. On Earth, microbial life arose under those conditions. Did the same happen on Mars? [More at link]