Scouring Mars for answers to life on Earth

We are seeing a gro­wing num­ber of mis­sions to Mars. Why is there so much inter­est in the red planet ?

Juliette Lam­bin. There is a lot of talk about it at the moment because seve­ral mis­sions to Mars are coin­ci­ding with one ano­ther. This is because the opti­mal launch win­dow occurs once eve­ry two years and only lasts a fort­night – so the mis­sions tend to all hap­pen at the same time. 

That said, Mars is a major object of stu­dy in “uni­verse science”. It is par­ti­cu­lar­ly inter­es­ting because it is smal­ler than Earth but was for­med at the same time. Also, in the begin­ning, condi­tions on Mars were quite simi­lar to those on our own pla­net. Name­ly, a dense atmos­phere, liquid water, a large-scale magne­tic field ; in other words, the neces­sa­ry ingre­dients for the emer­gence of a form of life. More than 3.5 bil­lion years ago, howe­ver, Mars lost all that and became almost fro­zen in time. As such, it remai­ned in more or less the same state that the Earth was in when life first appeared. 

From a scien­ti­fic point of view, what we are loo­king for on Mars are traces of fos­si­li­sed life. These are traces that can­not be found on Earth because there is no place as old as that, which has not been trans­for­med by ero­sion, plate tec­to­nics, over­run with modern acti­vi­ty, etc. So, loo­king for traces of life on Mars means loo­king for pos­sible traces of pri­mi­tive life on Earth ! Mars is the best and most acces­sible object of stu­dy for exo­bio­lo­gy : the stu­dy and unders­tan­ding of eve­ry­thing that can lead to the appea­rance of life. 

The aim of this pro­gramme is to take samples of the Mar­tian soil and bring them back to Earth for ana­ly­sis using ter­res­trial means.

How will the Mars Sample Return mis­sion and the arri­val of the Per­se­ve­rance rover on Mars contri­bute to these studies ?

The rover, Per­se­ve­rance, is the first of seve­ral mis­sions contri­bu­ting to the Mars Sample Return (MSR) pro­gramme, car­ried out by the Ame­ri­cans in asso­cia­tion with Europe. The aim of this pro­gramme is to take samples of Mar­tian soil and bring it back to Earth for ana­ly­sis that will be com­ple­ted around 2030. Up to now, mis­sions have main­ly been car­ried out in orbit around the pla­net using satel­lites, fol­lo­wed by robo­tic explo­ra­tions with the rovers that have lan­ded. These mis­sions have pro­vi­ded a good des­crip­tion of the topo­gra­phy, com­po­si­tion of the atmos­phere and geo­lo­gy of the sur­face of Mars. We have alrea­dy detec­ted ice caps and iden­ti­fied geo­lo­gi­cal struc­tures that look like runoff, which could be cau­sed by liquid water that would have flo­wed on the sur­face Mars in the past. 

The twin rovers, Spi­rit and Oppor­tu­ni­ty, laun­ched in 2003 as part of the Mars Explo­ra­tion Rover mis­sion, as well as the Curio­si­ty rover of the Mars Science Labo­ra­to­ry mis­sion laun­ched at the end of 2011, chan­ged the game because they could move. In addi­tion to cli­mate ana­ly­sis, Curio­si­ty’s main objec­tive was to deter­mine the past habi­ta­bi­li­ty of Mars based on the ana­ly­sis of rocks and mine­rals. The Per­se­ve­rance rover is more auto­no­mous than pre­vious rovers and its mis­sion is dif­ferent. Not only will it search for pos­sible bio­si­gna­tures, but it will also take samples and place them in sea­led tubes from seve­ral loca­tions. They will then be retrie­ved and brought back to Earth where they will be analysed.

Why can’t these samples be ana­ly­sed direct­ly on Mars ?

Because of the constraints of mass, volume and auto­no­my. A Mar­tian rover car­ries very sophis­ti­ca­ted ins­tru­ments, but they are minia­tu­ri­sed and there are not many of them – only 7 on Per­se­ve­rance, for example. The search for life, dating of rocks and fine mine­ral ana­ly­sis all require ins­tru­ments that they can­not be sent to or ope­rate on Mars. Some bio­lo­gy or bio­che­mis­try expe­ri­ments involve so many expe­ri­ments and com­pli­ca­ted steps that only they can only be done by scien­tists, using sen­si­tive equip­ment only found back on Earth. 

In order to ana­lyse the samples brought back, there must also be a strict seal pro­to­col. Hence, samples will be qua­ran­ti­ned in high bio­lo­gi­cal safe­ty labo­ra­to­ries (P4 type) and pro­tec­ted from any bio­lo­gi­cal or che­mi­cal conta­mi­na­tion by ter­res­trial com­pounds. The first qua­ran­tine stu­dies will also seek to detect any pos­sible Mar­tian life forms or bio­lo­gi­cal risk agents.

What is the role of CNES in the Mars Sample Return programme ?

CNES is res­pon­sible for the entire French contri­bu­tion to this pro­gramme in coope­ra­tion with NASA. We work in close col­la­bo­ra­tion with CNRS scien­tists, who deve­lop the scien­ti­fic ins­tru­ments and stu­dy the data from the expe­ri­ments, and with indus­trial part­ners. In Tou­louse, CNES is home to the FOCSE for “French Ope­ra­tion Cen­ter for Science and Explo­ra­tion”. This centre, which alrea­dy ope­rates the equip­ment of rovers from the pre­vious gene­ra­tion, in par­ti­cu­lar the Chem­Cam (CHE­Mis­try CAMe­ra) and SAM (Sample Ana­ly­sis at Mars) came­ras, ensures the ope­ra­tion of the Super­CAM instrument. 

Eve­ry day, the Tou­louse team ana­lyses the data recei­ved the day before and, after coor­di­na­ting with the people in charge of the pro­gramme at the Jet Pro­pul­sion Labo­ra­to­ry (JPL) in Pasa­de­na, Cali­for­nia, sche­dules the expe­ri­ments conduc­ted by the Fran­co-Ame­ri­can ins­tru­ments on board Curio­si­ty and Per­se­ve­rance. With trans­mis­sion times bet­ween Earth and Mars varying bet­ween 4 and 20 minutes and pat­chy visi­bi­li­ties, the Mar­tian rovers are not direct­ly remote-control­led. They are control­led by sen­ding dai­ly pro­grammes which are then auto­ma­ti­cal­ly sent out. The pro­grammes are writ­ten by the teams of each ins­tru­ment, then che­cked and assem­bled at the JPL, which sends them. We work on US West Coast time. Even though we often start at 10PM and finish at 4AM, it’s a fan­tas­tic way to work from Tou­louse, France, to pilot a robot on Mars.

Interview by Sophy Caulier