Was there life on Mars?

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After traveling more than six months in space, NASA’s latest rover landed on the red planet February 18. The explorer craft touched down in an area that may have hosted life on what was once a water-soaked Mars billions of years ago. The planet is now a frozen desert.

Decades in development, the Perseverance rover is equipped with everything it needs to traverse the edge of an ancient lake bed, Jezero Crater, searching for microscopic evidence of ancient life.

It was no simple voyage. The trip to Mars took Perseverance 203 days to travel 293 million miles to reach the planet.

At that distance, communications between the lander and ground control take 11 minutes to transmit. Radio waves can only move at the speed of light, so at this distance the lag applies to even the speediest transmissions. This meant the spacecraft needed to navigate and decide on its own where to land based on the mission.

The lander, despite these challenges, successfully entered Mars’ thin atmosphere, lowering Perseverance safely onto the rocky surface.

This wasn’t NASA’s first rodeo. To date, the space agency has safely landed nine times on Mars. Perseverance marks the fifth time NASA has landed a rover.

Over the years, other space agencies also have ventured to the red planet. Voyages from Earth to Mars conducted by the European Space Agency, the space program of the former Soviet Union (now the Russian Federation’s Roscosmos) and more have gone on since the ’60s.

To date, there have been seven attempts outside of NASA to land on Mars. Of those attempts, though, only one — Mars 3 — from the former Soviet Union was successful in 1971.

The Perseverance rover made history by landing in the previously unexplored Jezero Crater.

Welcome to the rock

The western edge of the Isidis Planitia, a plain 930 miles (about 1,500 kilometers) wide that was left by an impact more than 3.9 billion years ago, was Perseverance’s target. Now known as Octavia E. Butler Landing, this site would be the most challenging maneuver NASA had ever executed. The crater’s rocky terrain required use of autonomous software and active radar that calculated the ideal surface to land, hands-free.

Only 11 minutes later would NASA know of the rover’s successful landing.

After two months of getting situated in its new home, Perseverance is ready now to execute its stated mission: searching for life on the barren planet. And its companion helicopter, Ingenuity, will test the first powered, controlled flight on another planet.

Looking ahead, the rover has a few paths it can take. The team at NASA chose this site due to its geologically rich terrain. This arid ridge line shows its history as a 3.9 billion-year-old river delta. Along this riverbed, Perseverance can sample rocks as varied as clays and carbonates that may contain clues to ancient microbial life.

But where to begin? The rover could roll out from the Butler landing and then head south along the yellow path, or potentially head north along the purple path. Each route is around a 3-mile journey, and these paths would bring it back toward higher ground. Passing the small crater Belva and the cliffside slopes, Perseverance could climb toward a river valley called the Neretva Vallis. As the rover journeys along, its onboard equipment will collect, study and store research samples.

Just a small sample

Perseverance is equipped for discovery unlike any rover before it.

Seven feet tall and 9 feet wide, nuclear powered and covered in 23 cameras, Perseverance can analyze its surroundings, record audio and send back stunning panoramas. But the rover’s ability to collect samples of Mars is what sets it apart.

Unlike its predecessors, Perseverance has a mounted arm that allows it to drill rock and soil. Below the rover’s chassis, in its “belly,” is a rotating carousel with a variety of drill bits.

The rover has 43 chances to seal away samples that may be key to understanding the ancient biology along the crater’s edge.

Once collected, samples will be kept in a storage rack within the rover for now. At a future date, the NASA mission team will decide when and where to store samples for future retrieval.

The prospect of these samples containing microfossils — preserved molecular life — would be big news to astrobiologists. Future missions will return the samples to Earth.

Discovery of microfossils would be an unprecedented moment in human history. Evidence of microfossils would show that planets outside our humble rock could have supported life — and make it clear life could exist elsewhere if the chemistry allowed it.

Such a finding may also show us that life can exist in a non-nucleic acid form, something beyond our current grasp besides the hypothetical.
Correction: A previous version of the map of Mars misstated the date of the Perseverance landing. It was February 18, 2021.