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