Nasa's Perseverance rover will scour Mars for signs of life

WASHINGTON • Nasa's most advanced Mars rover, Perseverance, launches from Earth on July 30, on a mission to seek out signs of ancient microbial life on what was once a river delta 3½ billion years ago.

The interplanetary voyage will last six months.

Should the SUV-sized vehicle touch down unscathed, it will start collecting and storing rock and soil samples, to be retrieved by a future mission and brought back to Earth in 2031.

Perseverance follows in the tyre tracks of four rovers before it, all American, first launched in the late 1990s.

Together with satellite and surface probes, they have transformed people's understanding of Mars, showing that the Red Planet was not always a cold and barren place.

Instead, it had the ingredients for life as we know it: water, organic compounds and a favourable climate.

Scientists will examine the samples obtained by Perseverance to look for fossilised bacteria and other microbes to try to confirm if aliens did once live on our neighbouring planet.

Nasa has been teleworking for months because of the coronavirus pandemic, but the launch calendar for this US$2.7 billion (S$3.7 billion) mission has not been affected.

"This mission was one of two missions that we protected to make sure that we were going to be able to launch in July," said Nasa chief Jim Bridenstine.

Earth and Mars are on the same side of the Sun every 26 months, a window that cannot be missed.

The United States is the only country to have successfully landed robots on Mars: Four landers, which are not mobile, and the rovers Pathfinder, Spirit, Opportunity and Curiosity.

Of the rovers, only Curiosity is still active, with the others left on the surface after their machinery failed or contact was lost.

It was only in the past two decades that it was confirmed Mars once had oceans, rivers and lakes.

Curiosity confirmed the presence of complex organic molecules - but its instruments are not capable of concluding that they were created by biological processes.

The first two landers, Viking 1 and 2, both looked for signs of life as far back as 1976, but haphazardly.

"At the time, the experiment for life detection was considered to be a complete failure," said Dr G. Scott Hubbard, who launched the current Mars exploration programme in the 2000s.

Nasa then decided to proceed in stages. By studying the soil, analysing the molecular composition of rocks, and carrying out satellite observations, geologists and astrobiologists gradually understood where water had flowed, and what areas could have been conducive to life.

"Understanding where Mars would have been habitable in the past, and what kind of fingerprints of life you're looking for, was a necessary precursor to then going, at significant expense, to this very well selected spot that would produce these samples," said Dr Hubbard.

On Feb 18 next year, Perseverance should land in the Jezero Crater, home to an ancient river that fanned out into a lake between three billion and four billion years ago, depositing mud, sand and sediment.

"Jezero is host to one of the best preserved deltas on the surface of Mars," said Dr Katie Stack Morgan, a member of the science team.

On our planet, scientists have found the fossilised remains of bacteria billions of years old in similar ancient deltas.

The six-wheeled rover is 3m long, weighs a tonne, and has 19 cameras, two microphones and a 2m-long robotic arm.

Its most important instruments are two lasers and an X-ray device which, when projected on rocks, can analyse their chemical composition and identify possible organic compounds.

Also on board is the experimental mini-helicopter Ingenuity, which weighs 1.8kg. Nasa hopes it will be the first chopper to take flight on another planet.

Perseverance probably will not be able to determine whether a rock has ancient microbes. To know for sure, the samples will have to be brought back to Earth where they can be cut into ultra-thin slices.

"Getting true scientific consensus... that life once existed on Mars, I think that would still require a sample return," said Dr Ken Williford, deputy head of the science project.

One thing we should not expect are the fossilised shells that people find on Earth, he added.

If life once did exist on Mars, it probably did not have time to evolve into more complex organisms before the planet dried up completely.

AGENCE FRANCE-PRESSE