The largest and most sophisticated vehicle ever sent to Mars will land on the red planet next week, beginning a two-year mission that will search for signs of life and prepare the way for future human visits.
All being well, on Thursday the $2.7bn Perseverance rover will touch down on Jezero Crater near the Martian equator to explore the planet’s surface and collect samples to be sent back to Earth. An ultralight on-board helicopter will also be launched in what would be the first powered flight on another planet.
“Perseverance is a huge upgrade on all the previous landers and rovers we’ve sent to the planet,” said Professor Andrew Coates, a University College London space scientist who has been involved in Mars missions for 20 years.
But the car-sized Perseverance must first survive what Nasa engineers famously called “seven minutes of terror” when the previous Curiosity rover landed in 2012. That is the time it takes to decelerate from the entry speed of 20,000kph, when the craft reaches the Martian atmosphere, to a touchdown that is slower than walking pace.
The technology deployed will be an upgraded version of that on Curiosity, with added safety features including a “range trigger” to guide the opening of the craft’s parachute and maximise the chance of a gentle touchdown.
To do so, Perseverance will have to cut itself free from its parachute and begin a rocket-powered descent — “a kind of jetpack with eight engines pointed down at the ground”, as Al Chen, the engineer responsible for descent and landing, put it.
The final phase will involve a “sky crane” lowering the rover to the surface on a set of cables. When the lander senses that its wheels have touched the ground, it cuts the cables connecting it to the descent vehicle, which flies off to crash-land a safe distance away.
Descent may only take seven minutes but mission controllers at Jet Propulsion Lab in California will not know for 11 minutes — the time taken for radio signals to travel 200m km back to Earth — whether Perseverance has landed safely.
Jezero Crater has been chosen as the drop site because the Nasa scientists believe it is one of the best places on Mars to search for signs of ancient microbial life. More than 3bn years ago, when water flowed on Mars, it was a lake, fed by a river with a delta.
Perseverance will journey around the ancient and now desiccated terrain, armed with instruments to dig and probe the rocks and soil — physically and chemically — for fossilised signs of ancient life. Scientists do not expect to find living organisms.
An aerial view of the crater will be provided by the Ingenuity helicopter, weighting just 1.8kg, which is scheduled to make five test flights. It is not part of the primary science mission but what Nasa calls a technology demonstration, to show how well a rotorcraft can perform in the Martian atmosphere which is just 1 per cent as dense as Earth’s.
Another forward-looking technology experiment is the toaster-sized Mars Oxygen In-Situ Resource Utilization Experiment, or Moxie, which will make oxygen out of Mars’ thin air by electrochemically breaking down carbon dioxide. If astronauts are ever to land and live on the red planet they would need locally generated oxygen to breathe and an ingredient for fuel.
Perseverance will also leave a legacy on the Martian surface for future missions. Its Sample Caching System will put broken rock and dust into metal canisters and leave them behind to be collected and brought to Earth by future missions that Nasa is planning in collaboration with the European Space Agency.
Some time in the early 2030s, they hope, scientists will be able to analyse these samples in terrestrial labs using equipment far too large and complex to send to another planet.
It is possible that Perseverance — or the Rosalind Franklin rover due for launch next year as part of Europe’s ExoMars mission — will by then have found signs of past or even present life on Mars. Perseverance is looking among other things for geological evidence of stromatolites, layered deposits built up by microbes in the ancient Jezero lake.
But confirmation might have to wait a few years for laboratory examination of the samples to return to Earth. “Even if we find no evidence at all of life, that would be important,” said Ken Farley, Perseverance project scientist. “We would have done a deep exploration of a habitable environment and shown it has not been inhabited.”
If, on the other hand, unmistakable evidence for biological activity was found on the one habitable planet that has been investigated beyond Earth, scientists could draw only one conclusion: the universe is teeming with life.