T HE IDEA , popular in science fiction, that alien life will do bad things to life on Earth if the two come into contact, is not restricted to the activities of malevolent extraterrestrial intelligences. In “The Andromeda Strain”, a novel by Michael Crichton, the baddies are mysterious and deadly (but completely unintelligent) microbes that hitch a ride to Earth on board a military satellite. They start by killing everyone in the town of Piedmont, Arizona, and then wreak havoc in a secret underground government laboratory, as scientists struggle to understand and contain them.

Move one state north, to Utah, and at least part of that fiction may, some hope, soon become true. For Utah is the planned landing place of the first samples to be collected from the surface of Mars. Optimists like to think that those samples might contain traces, even if only fossil, of life on Mars. And in case they do, the samples’ ultimate destination will be a purpose-built receiving facility with level-four biosafety controls—the highest category possible.

The Mars Sample Return ( MSR ) mission intended to achieve all this will require three launches from Earth over the course of a decade, and five separate machines. The organisations involved—America’s National Aeronautics and Space Administration, NASA , and the European Space Agency, ESA —are each responsible for specific craft in the chain of what David Parker, ESA ’s head of human and robotic exploration, calls “the most ambitious robotic pass-the-parcel you can think of”.

Delta force

On December 11th, at a meeting of the American Geophysical Union in San Francisco, space scientists and astrobiologists outlined the details of the MSR . The project will begin with the launch, next July, of NASA ’s Mars 2020 mission. This will carry to the planet a successor to Curiosity, a rover that has been crawling productively over the Martian surface since 2012. The Mars 2020 rover, yet to be named, will land in a 45km-wide crater called Jezero, in February 2021. Its main purpose is to search for signs of ancient microbial life. Around 3.5bn years ago, Jezero contained a lake. Mars 2020 will drill for samples from the clay and carbonate minerals now exposed on the surface of what used to be a river delta flowing into this lake (visible top right in the picture).

When the rover finds something that its masters want to bring back to Earth, it will hermetically seal a few tens of grams of the material in question into a 6cm-long titanium test tube, and then drop the tube on the ground. It can deal in this way with around 30 samples as it travels to different parts of the crater. Once it has dropped a tube it will broadcast that tube’s location to the Mars Reconnaissance Orbiter, a satellite already on station that is armed with a high-magnification camera. This camera will take photographs of the tube and its surroundings, so that the tube can be found at a later date. The tubes are intended to be able to survive for more than 50 years on the surface of Mars, at temperatures less than 20°C.

The next phase of the project will begin in 2028, when a “fetch rover” designed and built by ESA will be sent to Mars to find and collect the tubes. This rover will be small, nimble and ten times faster than any of its predecessors. It will also be semi-autonomous, which will permit it to spot, pick up and manoeuvre the test tubes into the interplanetary equivalent of a test-tube rack without detailed instructions from Earth.

Once the fetch rover has collected all the tubes, it will deliver the rack to a NASA -built craft called the Mars Ascent Vehicle ( MAV ). This rocket will have arrived from Earth, filled with fuel, in the same mission as the fetch rover. Once it has the samples, it will launch itself from the surface of Mars—the first ever rocket launch from a planet other than Earth.

Once in orbit, the MAV will throw its basketball-sized payload overboard. Waiting nearby to intercept the cargo will be yet another craft, the Earth Return Orbiter ( ERO ), built by ESA . This will have been launched from Earth independently of the MAV -and-fetch-rover mission. The ERO will find, ingest and seal the payload, to avoid contaminating it with any organisms that might have hitched a ride all the way from Earth. Using a gentle, solar-powered electric propulsion system, the ERO will then take the payload back to Earth over the course of the subsequent few years.

When the ERO eventually goes into orbit around Earth (which will be in 2031, at the earliest) it will release the payload. This will be packed into a special, dome-shaped Earth Return Vehicle designed to carry the samples safely through the ferocity of atmospheric re-entry to a landing in the desert of Utah—whence they will be taken to their new bio-fortified home for examination. Once examined and deemed safe, the samples will then be distributed to researchers around the world for study.

Lakeside view

It is, then, an extraordinary enterprise. But all of this complexity does raise the question of why researchers would go to so much effort to collect Mars rocks. The answer, as Michael Meyer, the scientific boss of NASA ’s Mars Exploration Programme, told the conference, is that although, when you are on another planet, you have to hand all the rocks that you could ever want, you are also stuck with the handful of instruments that you took with you to look at them. Using sophisticated X-ray scanners or grinding samples up and feeding them through a chemistry set is not an option.

It is true that Martian rocks are already available for study, in the form of 200 or so meteorites that have arrived on Earth after having been blasted from the Martian surface by asteroid impacts. However, though these are geologically valuable they have little to offer about any putative Martian biology because they have spent millions of years travelling through the harsh conditions of space, being bombarded by radiation that will probably have destroyed any complex molecules within them that were made by living things.

A sample-return mission will not be cheap. Researchers from NASA and ESA , who have established a working group to harmonise technical efforts for the various stages of the project, estimate it will cost $7bn to complete. ESA already has approval for some of its parts. When ministers from its 22 member countries met in November to discuss the agency’s next three-year budget, they agreed to make €450m ($500m) available to pay for the project’s early stages. For its part, NASA expects to hear about funding for MSR in February 2020, as part of next year’s federal budget.