The 3 places NASA could hunt for signs of ancient life on Mars in 2020
If you send a rover to Mars, you need to figure out what you want to study once it gets there.
Do you want an up-close look at former hot springs? Are you interested in learning more about the planet's past volcanic activity? How about checking out a crater that was once filled with water?
These are the questions NASA is asking right now as it prepares to send a rover designed to hunt for signs of past life on Mars by 2020.
Scientists working with the space agency have narrowed down a list of possible landing sites to the final three. Now, NASA just needs to figure out which one to choose.
One possible landing site -- the Jezero crater -- is thought to have a wet past.
About 3.5 billion years ago, rivers on Mars sloshed water into the crater, making it a lake.
"Scientists see evidence that water carried clay minerals from the surrounding area into the crater after the lake dried up," NASA said in a statement.
"Conceivably, microbial life could have lived in Jezero during one or more of these wet times. If so, signs of their remains might be found in lakebed sediments."
If the 2020 rover -- which is also expected to cache rock samples for a future mission that will return them to Earth -- does land in the crater, it won't be the first time a NASA spacecraft has explored a previously wet crater on Mars.
At the moment, the space agency's Curiosity rover is roaming around Mars' Gale crater, and has found that at least part of the planet could have once been habitable for microbes.
While the 2020 rover won't have the chance to visit Curiosity's part of Mars, it may land on a part of the red planet already explored by NASA's Spirit rover.
Spirit found that springs of water may have once sprouted from Columbia Hills in the Gusev crater, so it's possible that the 2020 rover will land there to more fully investigate what Spirit found.
"After the rover stopped working in 2010, studies of its older data records showed evidence that past floods that may have formed a shallow lake in Gusev," NASA said.
That watery crater could have also preserved signs of past life in its ancient past.
The third possible landing site, in the northeast part of Syrtis Major, is thought to have been volcanically active in the ancient past.
"Microbes could have flourished here in liquid water that was in contact with minerals," NASA said. "The layered terrain of NE Syrtis holds a rich record of the interactions that occurred between water and minerals over successive periods of early Mars history."
The 2020 rover -- which will carry seven science instruments to Mars -- will be a car-sized spacecraft modeled somewhat on Curiosity.
The rover is expected to launch to the red planet in July 2020 from Cape Canaveral Air Force Station in Florida, and NASA should pick its final landing site for the rover about a year or more before that launch date.
Between now and then, NASA will continue to evaluate the three candidate landing sites to see which ones are safest and most rich for exploration.
Miriam Kramer worked as a staff writer for Space.com for about 2.5 years before joining Mashable to cover all things outer space. She took a ride in weightlessness on a zero-gravity flight and watched rockets launch to space from places around the United States. Miriam received her Master's degree in science, health and environmental reporting from New York University in 2012, and she originally hails from Knoxville, Tennessee. Follow Miriam on Twitter at @mirikramer.
