A mission will deliver rock and soil from Mars to laboratories on Earth in the 2030s. Mars Sample Return (MSR) is led by Nasa with participation from the European Space Agency (Esa). The mission will allow scientists to use the best laboratory instruments on Earth to determine whether Mars hosted microbial life billions of years ago.
Author
- John Bridges
Professor of Planetary Science, University of Leicester
So what will happen to the samples once they arrive on Earth?
Nasa's Perseverance rover has already been doing the hard work of collecting the samples. The rover has been exploring a Martian location known as Jezero Crater since landing in February 2021. Along the way, it has used its drill to extract cores - cylindrical samples of rock - from Martian rocks, depositing them in sample tubes on the floor of the crater.
Present day levels of cosmic radiation at the Martian surface are thought to be too high for life to survive there. However, conditions may have been more hospitable to life billions of years ago, and it is these potential traces of ancient life that Perseverance was designed to seek out.
In September 2023, an independent review board found MSR's budget and schedule to be "unrealistic," and said that this would potentially delay the mission's launch beyond 2028. This has led Nasa to seek alternative approaches to carrying out the mission.
The space agency issued a call for ideas from industry and is currently studying two proposals. But in terms of the broad mechanics, something - a rover or small helicopter - will need to collect the sample tubes and deliver them to a vehicle. That vehicle will then blast off the surface of Mars.
A capsule, carrying those Martian samples, will eventually enter the Earth's atmosphere and parachute down to a government facility in Utah, US. This is all projected to happen in the 2030s.
Once safely on Earth, the samples from Jezero Crater will be analysed using sensitive instruments that are too big and complex to send on a rover to Mars. That's the essence of MSR: in order to unambiguously identifying any traces of ancient Martian life, scientists will need to carry out multiple experiments and replicate the results.
In other words, separate and independent scientific teams will have to show that they can get the same outcomes from those experiments.
The scientific community is still making new discoveries with the 380kg of rock and soil from the Moon that was delivered to Earth by the six Apollo missions over 50 years ago. In the Apollo era, scientists had to work out a plan to keep the Moon samples pristine, in order to preserve them for generations of scientists to study.
Their solution was to put them in glove boxes: sealed containers that allow users to manipulate the contents via long gloves that extend from the outside to the inside of the box. These glove boxes contain dry nitrogen gas that protects against chemical changes to the samples. That's worked well for the Moon rocks; the Apollo 11-17 samples can be seen and studied at Nasa's Johnson Space Center in Houston today.
A more challenging plan will be needed for the approximately 500g of carefully selected Martian rock and soil. The facilities in which they are eventually stored will need to carefully control factors such as humidity and temperature. They will also need to prevent the samples from being contaminated by terrestrial microbes.
The requirements for managing the Martian samples are decided by an organisation called the Committee on Space Research (Cospar). Under Cospar guidance, MSR is defined as a Category V Restricted Earth Return Mission.
While scientists do not generally expect the Martian samples to contain present-day life, the requirements mean that the samples will be treated as if they do until the possibility is excluded. Cospar says : "A program of life detection and biohazard testing, or a proven sterilisation process, should be undertaken as an absolute precondition for the controlled distribution of any portion of the sample."
Thus, a major part of MSR planning is the design and construction of a sample receiving facility (SRF), a building where initial analyses of the rock and soil are to take place. The work will be conducted under strict biocontainment rules , which mean that scientists will use equipment and follow procedures usually deployed in some of the most world's most secure labs, designed to study harmful bacteria and viruses such as Ebola and Marburg virus. This situation will persist until a "sample safety assessment" has taken place.
This safety assessment will determine whether the samples can be studied at lower levels of biological containment. Only after that stage and another called "basic characterisation", where scientists carry out an initial study of the minerals and chemistry of the rocks, will the samples gradually be released to the wider scientific community.
One problem for the mission is the complexity and cost of the SRF, which is expected to rise to hundreds of millions of dollars, or euros. This is largely because of the need to not only comply with the Cospar rules but also to incorporate the range of microscopes and spectrometers needed for the analyses.
Much of the reason for the delays in delivering the overall MSR programme come down to cost, so there is currently pressure to reduce the price tag. Against this background, Nasa and Esa have convened a measurement definition team , a panel of scientists who will determine which analyses are needed within the SRF. The resulting report will be published shortly.
In parallel, a programme of work to design and build new technology for MSR that allows both biological containment and analysis of the minerals in Martian samples is taking place. Esa, with Nasa collaboration, is funding the design of secure chambers called multi-barrier isolator cabinets, inside which the Martian rock and soil can be studied.
These cabinets will also incorporate the range of different scientific instruments needed for the basic characterisation stage. These could include powerful microscopes and a Raman spectrometer .
Combining the requirements for containment and analysis in this way has the potential to not only reduce the time needed before samples can be released to the scientific community, but also to substantially reduce the costs of the SRF and thus help the overall MSR programme.
John Bridges of Space Park Leicester, University of Leicester is funded by the European Space Agency and UK Space Agency to design and build isolator, spectroscopic and portable technology for Mars Sample Return at Space Park Leicester. He is a member of the NASA-ESA MSR Measurement Definition Team.
