Red-rock return

A joint ESA/NASA mission to return rock samples from Mars will push both robotic and human collaboration skills to the limit. Jon Excell reports.

As scientists pore over the data gathered by NASA’s Phoenix Mars Lander, and marvel at the confirmation that water exists beneath the Martian soil, international researchers are planning the next step in the exploration of the red planet: an audacious, multi-billion dollar interplanetary robot relay that will collect samples of Martian rock and return them to earth for analysis.

A recent report by iMARS, a group of international scientists and engineers studying the Mars sample return, revealed plans for a joint ESA/NASA mission that will build on the successes of both agencies’ Mars explorations, such as the forthcoming ExoMars and Mars science laboratory missions.

It will begin in 2018 with the launch of a rocket that will send a rover and an ascent vehicle to the surface of Mars. A year later, a second rocket carrying an orbiter will be launched. In 2020 the ascent vehicle, loaded with samples of rock collected by the rover, will leave Mars and deposit the sample container in Martian orbit. Once there, it will be picked up by the orbiter, which will head back to Earth, passing the sample on to a specially-developed vehicle that will protect it from the extreme temperatures of re-entry.

Leicester University’s Dr John Bridges, who helped draw up the iMARS report, said the participants’ roles are likely to reflect current areas of expertise, with the US developing the systems for entry, descent and landing, and Europe the Rover and the orbiter.

The UK, with its strong heritage in robotic space exploration, is set to play a starring role. A top candidate for the development of the rover is Stevenage’s EADS Astrium, prime subcontractor for the robotic rover that will be at the heart of ESA’s ExoMars mission, scheduled for launch in 2013.

The prototype, named Bridget, has been designed to function as a mobile laboratory as it travels many kilometres over the surface of Mars.

Dr Ralph Cordey, development manager for space science and exploration at EADS, believes the plucky rover will be able to perform many of the functions required by a Mars sample return mission, ranging far and wide to hunt for samples and even using its robotic manipulators to transfer samples into containers within the ascent vehicle.

In a separate project, Astrium has been investigating the development of an autonomous rendezvous system that would enable the orbiter to collect the sample container once it has been deposited in orbit. ‘The need is to locate a little canister, weighing 5kg and measuring 10-15cm across, that will have been carried up from the surface of Mars by the ascent vehicle,’ said Cordey. ‘Your mother spacecraft will have to find it somewhere in the dark starry sky using optical sensors and microwave techniques, home in on it by adjusting its orbit, then finally bring it in on board.’

Beyond the key elements of the sample return mission, Bridges said the UK could also play a major part in the analysis of the samples once they arrive back on earth, with its world-leading expertise in space science making it a prime candidate for one of two planned sample return facilities.

A big issue will be ensuring any facility is secure enough to prevent any bugs or microbes that may inhabit the Martian rock from escaping and contaminating the earth. But Bridges played down those fears, claiming the scientific benefits will far outweigh the risks of interplanetary infection.

He said the chief scientific advantage of bringing samples back to earth is that they can be subjected to tests that are beyond the capability of in-situ robotic probes.

‘We will be able to use the most sophisticated instrumentation available. Even with improvements in robotic missions you’re not going to get to, for instance, the fullest characterisation of organic components,’ he said.

‘What you might call bread-and-butter stuff in terrestrial labs, like looking at the texture of rocks, is incredibly difficult to do robotically because you need to cut up rocks, slice them and carry out micron- scale mineral analysis.’

Bridges said such tests will enable scientists to learn about the mantle and crust evolution of Mars, which could shed light on our planet’s evolution.

But to reap these scientific rewards, all involved in the mission will have to ensure that a project involving dozens of robotic systems, and a loose-knit alliance of countries not always used to working together, operates without a single error over its five-year lifespan.

If they can pull it off, it will be as much of a triumph for international collaboration as it will for robotic space exploration. Astrium’s Cordey said: ’There are many areas that need to be examined in detail in order to come up with a design that will actually work — how the temperature of the fuel behaves on the surface of Mars, the need for autonomy in a rover, the fact that we will need it to cover significant distances — the overall scale is mind-boggling.

’A mission like this has many elements and we have to ensure that when they’re behaving as an end-to-end system the likelihood of them all working together is sufficiently high that an overall mission success is guaranteed.

‘This mission will involve a sequence of robotic activities: gathering a sample, manipulating a sample, launching a sample, rendezvousing with the sample, manipulating it again on a spacecraft and bringing it back to earth. What we have to do is to really get a grip on the best way to ensure overall mission success.’

Bridges is confident that despite this level of complexity, the desire of all involved to make it happen is the best guarantee of success. ‘It’s a high-priority mission — it chimes exactly with what NASA, ESA and many UK scientists and engineers want to do. It’s going to be a long process, but the signs are encouraging.’