A rover and a tiny helicopter are preparing to land on Mars, aiming to offer an opportunity to answer an enduring question: has life ever emerged on another planet?
Nasa’s ninth mission to descend on the cold, dry, red planet will be steered by a $2.7bn (£2.1bn), car-sized, six-wheeled rover christened Perseverance, which is expected to touch down on Thursday following a seven-month journey.
Previous Mars missions including Curiosity and Opportunity have suggested Mars was once a wet planet with an environment likely to have been potentially supportive of life billions of years ago. Astrobiologists hope this latest mission can offer some evidence to prove whether that was the case.
Perseverance is carrying a clutch of instruments designed to analyse rocks for biosignatures – chemical hallmarks of life – and will also store other samples from the planet’s surface. Future missions fuelled by Europe and the US will retrieve these samples and return them to Earth.
The emergence of life on Earth is an extraordinary event that is not fully understood, and ancient Mars had a much more benign climate than it has now, with many of the same raw materials that were available on Earth, noted Colin Wilson, a physicist at Oxford University.
“Of all the steps needed to develop life, how many occurred on Mars? This [mission] tells us not only about whether we’re alone in the solar system but also about how likely we are to find life in the thousands of other planets being discovered around other suns – so [it] has truly cosmic implications,” he said.
Apart from new instruments and an upgraded autopilot system, engineers have given Perseverance the ability to deploy a diminutive helicopter. Called Ingenuity, the 1.8kg drone-like rotorcraft is the first flying machine ever sent to another planet, and could serve as a “pathfinder” to discover inaccessible areas or as a scout for future rovers.
Mission controllers are steering the rover – which weighs more than a tonne –towards the 28 mile-wide (45km) Jezero crater north of the planet’s equator. The site was chosen for its promise for preserving signs of life: it was once home to an ancient lake and river delta that may have collected and buried microbes and locked them within rocks.
But with its low gravity and rarefied atmosphere, Mars is hardly a hospitable destination. More than half of the spacecraft sent there have blown up or crashed owing to hardware or software mishaps. Nasa’s new generation of rovers, including Perseverance, rely on a rocket platform called a sky crane to lower it on to Mars’s surface.
Perseverance is barrelling towards Mars at around 12,400 miles per hour; when it hits the top of the atmosphere, a heatshield slows it down to about a tenth of this speed. Then a supersonic parachute will pop out of the rover and reduce its speed to a few hundred miles per hour.
At that point, descending under the parachute, Perseverance will still be travelling far too fast to land safely. So it will then have to cut itself loose from the parachute and use rocket thrusters to slow down further. The thrusters will be used to hover roughly 20 metres above the surface, and the rover is then lowered by cables to the surface using the sky crane. The crane itself will then fire its rockets to crash at a safe distance.
Things can go wrong at multiple junctures. After covering hundreds of millions of miles, the rover needs to perform all landing autonomously. No corrections are possible because the long distance means any signal travels for several minutes, noted Susanne Schwenzer, an astrobiologist at the Open University.
Wind could divert the landing craft, especially in the parachute phase. The Martian surface itself, which can be strewn with boulders and contain sand patches and dunes as well as slopes and canyons, could be another obstacle in finding a safe landing spot, she said.
But, if all goes as planned, radio signals confirming success will be sent, followed shortly afterwards by the first images from the rover. Perseverance is scheduled to stick around for at least one Mars year – two Earth years.
“I am happily nervous in anticipation of the words ‘we are safe on Mars’,” said Schwenzer. “Having watched the Curiosity landing live, and knowing it can work, makes me optimistic, but of course, landing on another planet … is never easy, never routine.”
Apart from Nasa, missions from the UAE and China to Mars also kicked off last year. In 2023 the European Space Agency is expected to land on Mars its Rosalind Franklin rover, which will carry a drill capable of reaching metres below the surface, where biomolecules may survive protected from the harsh conditions above.
Schwenzer said that if indications of life were discovered on Mars – and there was a huge responsibility on scientists to be sure – “it would be the most exciting finding since the insight that the Earth is not flat”.