Nasa Rover Perseverance, has reached a watershed moment in its mission.
The six-wheeled robot will begin its ascent up an ancient delta feature in the crater where it landed on Tuesday.
It will roll uphill, occasionally stopping to inspect rocks that appear to have the best chance of preserving evidence of past life on the planet.
Perseverance will collect some of these rocks on its way back down, depositing the samples at the delta’s base for later missions to retrieve.
The goal is to return this material to Earth in the 2030s for a thorough examination.
“The delta in Jezero Crater is the main astrobiology target of Perseverance,” said Dr. Katie Stack Morgan, deputy project scientist.
“These are the rocks that we believe have the greatest potential for containing signs of ancient life, as well as telling us about Mars’ climate and how it has evolved over time,” she said.
Last February, the rover made a spectacular landing in the middle of Mars’ 45km-wide Jezero Crater.
Nasa Rover Perseverance has been testing its tools and instruments, flying an experimental mini-helicopter, and getting a general sense of its surroundings since then.
But the robot’s main reason for visiting the near-equatorial bowl on Mars has always been to study the massive mound of sediments west of Jezero.
Based on satellite imagery, Perseverance’s preliminary ground observations have confirmed this assessment.
A delta is a structure formed by the silt and sand deposited by a river as it enters a larger body of water. The sudden slowing of the river’s flow allows anything carried in suspension to fall out.
The larger body of water in Jezero’s case was most likely a crater-wide lake that existed billions of years ago.
“Rivers that flow into a delta will obviously bring nutrients, which are beneficial to life. Then the fine-grained sediment brought and laid down at a high rate in a delta is beneficial to the preservation,” explained mission scientist Prof Sanjeev Gupta from Imperial College London, UK.
“In addition, if there is life in the hinterland, it can be carried down the river and concentrated in a delta.”
Perseverance has recently maneuvered itself to an “on-ramp” to the delta known as Hawksbill Gap. This gentle incline will raise the robot a few tens of meters above the crater floor.
The ascent is described as a reconnaissance mission. Perseverance will go on a “walkabout” in search of the most enticing delta rock. Some of the outcrops are exquisitely layered and fine-grained.
“The rover has an amazing suite of instruments that can tell us about the chemistry, mineralogy, and structure of the delta by examining sediments down to the scale of a grain of salt,” Purdue University’s Prof Briony Horgan said.
“We’ll learn about the chemistry of this ancient lake, whether its waters were acidic or neutral, whether it was a habitable environment, and what kind of life might have existed there.”
To be clear, no one knows if life ever began on Mars, but if it did, Perseverance’s choice of three or four rocks to drill and cache on the way back down to the crater floor could be the ones to tell us.
As intelligent as its instruments are, it’s unlikely that the robot will be able to make any definitive statements. Even on Earth, it is known that microbial life has existed for billions of years, but evidence of its earliest fossilized forms is complex, if not contentious, to interpret.
Establishing the possibility of life on Mars will thus have to wait until the rover’s rock collection is returned to Earth for the type of rigorous investigation that only the largest laboratories can carry out.
“The assertion that there is microscopic life on another planet in our Solar System is massive. As a result, the proof must be tremendous as well, “Jennifer Trosper, Nasa’s Perseverance project manager, stated
“I don’t believe the instruments we have can provide that level of proof on their own. They can provide a level of ‘we believe this is it,’ and then we bring the samples back to Earth and use the more sophisticated larger instruments here to confirm, “She said.
When Perseverance returns to the crater floor at the end of the year, it is expected to lay down its first rock stash.
This depot will include not only the rocks collected during the Hawksbill descent but also four samples collected on the crater floor in previous months.
In collaboration with the European Space Agency, Nasa is planning the missions required to go and retrieve the depot. Ventures, including another rover, a Mars rocket, and a carrier spacecraft, are expected to launch by the end of this decade.
Perseverance still has many years of work ahead of it. After laying down its first rock stash, it will drive back up Hawksbill Gap to the very top of the delta and beyond to see rocks that appear to be remnants of the ancient Jezero lake’s shoreline.
These deposits are composed of carbonate minerals and appear to have formed in an environment conducive to recording past life – if it ever existed.
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