With its bulky body, spindly legs, radioactive tail and a towering stalk with a single eye, Nasa’s latest Mars rover is not something you would want to come across on a dark night. Fortunately, we are standing in the warm California sunshine at the Jet Propulsion Laboratory (JPL) in Pasadena and this full-sized model of Nasa’s Mars rover is not going anywhere. It is, however, impressively substantial. The size of a family car, it looms beside us.

“It is very big,” says project scientist, Ken Farley. “The size is motivated by the need to drive across rugged terrain and carry a large number of science instruments.”

The Mars 2020 rover – named for its 2020 launch date – is based on the same basic structure as Nasa’s Curiosity rover. Since landing in 2012, Curiosity has notched up some 10 miles of exploration and is now, painfully slowly, making its way up 5.5km-high Mount Sharp.

“The rovers are capable of doing the same sorts of things – in the same way that if you have a pick-up truck you can look at lots of different applications,” says Farley. “We have a different set of science goals to Curiosity and different science instruments.”

As well as tougher wheels, an improved navigation and landing system and upgraded science payload, Nasa’s next generation Martian pick-up truck has one particularly intriguing attachment: a powerful percussive drill capable of extracting cores of soil, around the size of a stick of chalk, from the Martian surface. Each of these samples will be encapsulated in a tube, pulled into the rover by a robotic arm, capped and sealed.

“We’ll carry a collection of samples until we reach a place where we wish to deposit them,” says Farley, “and a future mission will come and pick them up.”

With evidence that Mars was once covered in water and shrouded in a relatively dense atmosphere, a fundamental reason to send missions to Mars is to search for signs of life. This plan to store a collection of cores is designed to help overcome the limitations of existing instrument technology.

“Looking for life is very hard to do with instruments we can presently fly,” says Farley. “We need the full complement of equipment we have in labs on Earth.”

The question is: how do they get them back to Earth?  

By the end of the mission, the Mars 2020 rover will have built-up a stash of around 35 samples – possibly containing compelling evidence for life. The question is: how do they get them back to Earth?

“This part of it hasn’t been worked out very well,” admits Farley. “There are ideas – some as simple as when the astronauts arrive at Mars, they will pick up the box and bring it back.”

“The notion that’s been best developed is that they’ll be a succession of missions that will follow,” he says.

These might involve a lander mission to collect the samples, put them into a rocket and fly that into the Martian orbit. This would be followed by a third mission to capture the cores from orbit and return them to Earth.

“If you want to send something to Mars and bring it back, whether that’s samples or humans, it’s very complicated,” says Farley. “If you look at movies like The Martian it all seems really easy; it isn’t easy.”

Nevertheless, Nasa has come a long way since its first Mars rover, Sojourner, rolled off the Pathfinder lander 20 years ago in July 1997. Just 65 cm long, the tiny solar-powered vehicle was only built to survive a week but ended up lasting 83 days. Pathfinder was followed by larger twin rovers Spirit and Opportunity in 2004, and then Curiosity eight years later.

As well as its sampling equipment, the Mars 2020 rover will come with another upgrade: an oxygen generator called Moxie – or Mars Oxygen In-Situ Resource Utilisation Experiment. This is designed to extract oxygen from carbon dioxide in the tenuous Martian atmosphere – technology which could one day provide oxygen for humans living in a Mars habitat.

But just as Nasa currently has no definite successor mission to Mars 2020 to bring the cached samples back to Earth, there is also no clear plan for landing humans to Mars  

“When we start to explore other bodies in the solar system, whether we go back to the Moon or onto Mars, to some extent we’re going to have to live off the land,” says retired Nasa astronaut Ron Garan, now Chief Pilot for space balloon company World View. “One of the many things these missions are doing is looking at using in-situ resources for space exploration.”

But just as Nasa currently has no definite successor mission to Mars 2020 to bring the cached samples back to Earth, there is also no clear plan for landing humans to Mars. Although Nasa’s stated ambition is to have the first human mission in the 2030s, this has yet to be funded by the US government.

“I think it’s going to be 10 to 20 years from the time we decide to go,” says Garan. “But if we never make that decision, if we never cross that line, it’s going to be an infinite amount of time to get to Mars – we’ve got to make that decision to go.”

In the meantime, the race is on to find evidence for past or present life on the red planet. And in that respect, the European Space Agency (Esa) in partnership with Russia may get there first.

A fraction of the size of the Nasa vehicle, Esa’s ExoMars rover is also due for launch in 2020. Unlike the US rover, the ExoMars rover will be able to drill two metres beneath the irradiated and eroded surface and analyse its samples on board.

If ExoMars finds evidence for life, then this could give Nasa the impetus – and, more importantly, political leverage – for a mission to get the Mars 2020 samples back to Earth and eventually astronauts landed on the Martian surface.

“When you think about sending humans to Mars, it seems like an incredibly complicated task,” says Farley. “But it would have looked very similar 20 years ago to landing a rover this big on Mars, and until people put their mind to it, nothing gets done.”

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