NASA’s long-awaited decision on where the Mars 2020 rover will touch down on the red planet has become the march madness of space exploration. This week, NASA crowned a champion and elaborated on how this mission will seek to achieve a feat no other Mars rover has done before.

On Monday, NASA’s Thomas Zurbuchen, the associate administrator of the Science Mission Directorate, told reporters that the Mars 2020 rover will touch down at Jezero Crater because it has the potential to illuminate details that answer a big question: Did ancient Mars harbor life? Ken Farley, Ph.D., the Mars 2020 project scientist at NASA’s Jet Propulsion Lab (JPL), added that the Jezero Crater — which spans 30 miles in diameter and was filled with water between 3.5 and 3.9 billion years ago — can yield a few different lines of evidence to answer that question. The Rover will prep that evidence (in the form of rock samples) so that NASA can bring it back to Earth in a followup mission.

NASA mars 2020
The location of jezero crater relative to two of the other landing sites considered. It's close, but was selected because it may hold important clues that illuminate whether Mars' harbored life billions of years ago.

“First, we want to seek evidence of possible ancient life on Mars, and second, we want to seek a diversity of rock types with which to explore the history and evolution of Mars,” Farley said. “We want to study those questions using the onboard instruments and also by preparing a suite of samples that could be brought back to Earth in the future.”

What Might We Bring Back?

Farley explains that Mars’ climate was very different roughly 3.5 to 3.9 billion years ago. During this time, the Jezero Crater filled with about 250 meters of water. This water flowed in through a river delta, where it may have deposited sediment, rocks and minerals at the bottom of this ancient lake.

“This is a major attraction from our point of view for a habitable environment,” Farley said. “Lakes on earth are both very habitable and inevitably inhabited. The second attraction is that a delta is very good at preserving biosignatures — any evidence of life that may have existed in the lake water, or at the interface between the sediment and the lake water, or possibly things that lived in the headwaters region that were swept in by the river.”

NASA river delta mars 2020
Jezero Crater, which was once an ancient lake, is adjacent to a former river delta that may have transported evidence of life.

When Farley says biosignatures, he’s referring to potential molecular markers that indicate a living thing was once there — this can be a variety of things but range from certain organic molecules to actual organic matter, either produced by a living thing or the remains of that living thing. This delta is attractive because it could be a one-stop shopping trip for these potential biosignatures. When water flowed through it millions of years ago, NASA scientists hope, it may have carried organisms or their cells from a variety of habitats along with it.

Farley adds that this location is rich in carbonate rock, which is produced when water, atmospheric gases (like carbon dioxide), and rock interact. Below the planet’s surface, Farley explains, there could have been an additional habitable environment.

But we may find something else there too. In February of 2017, scientists indicated that this carbonate rock might hold potential remnants of the ancient martian carbon cycle. On Earth, the carbon cycle helps to maintain the planet’s temperature. Ideally, in this martian carbonate rock, we might also find evidence of what Mars’ climate was like when it was able to support liquid water, and, maybe, life.

“We don’t actually understand why the climate was so different earlier on Mars,” Farley says. “We hope those carbonate rocks will tell us something about that.”

When Might These Samples Return to Earth?

Zurbuchen told reporters that they’re hoping for a sample return mission to launch sometime in the late 2020s. This mission would be tasked with entering the Jezero Crater and retrieving as many as 30 different rock core samples that the Mars 2020 rover will hopefully retrieve before leaving them at select locations for retrieval, called “cache depots.”

If all goes according to plan, this schedule should put the samples back on Earth in the early 2030s, by Zurbuchen’s estimate, though he couldn’t provide any further details on the sample return mission at this time. If NASA succeed, this will be a defining mission that sets us up for the next decade of research, Lori Glaze, acting director of NASA’s Planetary Science Division added.

“Mars 2020 will define the next decade of Mars exploration, enhance our understanding of the mars environment by in-situ research, and cache those samples on the surface for future scientific discoveries,” she said.

Photos via NASA (1, 2)