NASA officials have revealed their vision for what comes after the wildly successful Curiosity rover on Mars. Think of it as Curiosity Plus. Using Curiosity’s design as a starting point, Mars 2020 (as it’s currently known) will be another rover digging around the surface of the red planet. But, this time, rather than just looking for evidence that Mars was once habitable, the robotic explorer will be searching for signs of past life and packing up samples that, someday, will be returned to Earth for analysis.
“Curiosity has answered the question of whether Mars ever harbored a habitable environment,” said John Grunsfeld, NASA's associate administrator for science, at a July 9 press conference describing the new report. “Of all the options going forward…we really need to go back to the surface [of Mars] and do the next stage in answering the questions about potential past life on Mars: did Mars ever have life?”
The mission concept is pretty straightforward: find somewhere promising to land, learn about the geology of the region, then look for biosignatures—some evidence that life may once have hung out in the neighborhood. Potential biosignatures include detection of organic molecules, minerals produced by biological functions, or even very small fossils.
If Mars 2020 detects biosignatures while on Mars, NASA won’t pop the champagne and announce they’ve discovered extinct extraterrestrial life just yet. That next step will require getting a sample of the soil to Earth and interrogating it back home. “If that biosignature happens to be a dinosaur type bone,” said Grunsfeld, “we probably wouldn’t have to return that sample [to Earth]. But our understanding is that it’s likely to be microbial and that’s a darn hard measurement to make and a darn hard measurement to convince the skeptical scientist community.”
Mars 2020 will not deliver the samples itself. It will only select, acquire, and package them for later pick up. Who will do that task and when that will happen is unclear. NASA has no firm plans for a sample return mission and it’s not even clear who would get there first: robots or humans. But mission scientists are keen to separate the sample acquisition from the subsequent return to Earth. Researchers want to first ensure that they can remotely identify biosignatures as well as safely and reliably store biologically interesting samples. The problem of lifting those samples off the surface of Mars and retrieving them on Earth is left for a later mission.
NASA is not declaring this mission a search for life, current or extinct. Rather, they emphasize that they are looking for markers that may have been left behind by once living organisms. “We are not looking for the life that must have been there, because we don’t know the answer to that question,” said Jack Mustard, chair of the Mars 2020 Science Definition Team and Professor of geological sciences at Brown University. “But we’re saying, given the number of signs we’ve had, including what Curiosity is finding, that there is promise that had life been there and had left a mark in the geologic record, we want to be able to seek those signs.”
From here, mission scientists and engineers will analyze the report in detail and they hope to announce an open competition for instruments by this fall. The estimated cost, minus the launch vehicle, is $1.5 billion.