Voyage to Mars: myth or reality?

Who has nev­er dreamed of look­ing over the sur­face of Mars from the top of Olym­pus Mons, the highest moun­tain in the Sol­ar Sys­tem? Who would­n’t want to admire the blue sun­sets on the Red Plan­et at least once in their lifetime?

If the jour­ney between Earth and Mars is some­times no more than a page-turn­er in a sci­ence fic­tion nov­el, it is a dif­fer­ent story in real life. Com­plex, dan­ger­ous, uto­pi­an, sui­cid­al… there is no short­age of adverts from private com­pan­ies prom­ising the first man (or woman) on Mars by the end of the decade.

What are the obstacles to the explor­a­tion (dare we say, col­on­isa­tion) of Mars? Why aren’t we already reserving our liv­ing space near the slopes of Valles Mar­iner­is? Let’s take a look…

Unfor­tu­nately, the prob­lems will not start once we arrive on Mars, but long before. At present, humans have nev­er gone fur­ther than the lun­ar orbit, 3 or 4 days away from our plan­et. And even in these cases, if there is the slight­est prob­lem on board, or if no more com­mands respond, the immut­able laws of space mech­an­ics always man­age to bring the ship back to Earth by itself. This is what happened on 14 April 1970 when a liquid oxy­gen tank exploded in the Apollo 13 ser­vice mod­ule, end­ing the mis­sion. After three days of sur­viv­al in a ripped open space­craft, the astro­nauts were able to return safely to Earth.

Unfor­tu­nately, a scen­ario like this is unthink­able dur­ing a trans­fer between Mars and Earth. This jour­ney would last between 6 and 9 months, dur­ing which time the space­craft would become a truly autonom­ous world, cap­able of provid­ing water, oxy­gen and food to a crew sub­jec­ted to an envir­on­ment far more hos­tile than any­thing ever sim­u­lated or experienced.

In addi­tion to com­mu­nic­a­tions, which will become longer as the dis­tance between the space­craft and the con­trol centre increases, even­tu­ally reach­ing more than 10 minutes between the trans­mis­sion and recep­tion of a mes­sage, one of the main prob­lems con­cerns cos­mic rays, the flow of ener­get­ic particles (pro­tons, elec­trons, heavy atom­ic nuc­lei) that bathe inter­plan­et­ary space, irra­di­at­ing all objects in it. Although there are space envir­on­ments that today allow humans to train for long stays in space, such as the Inter­na­tion­al Space Sta­tion (ISS), the situ­ation is not the same. The ISS rotates at an alti­tude of 400 km, and in these con­di­tions it bene­fits greatly from the pro­tect­ive shield­ing effect of the Earth’s mag­net­ic field (the mag­neto­sphere), which slows down and deflects a frac­tion of cos­mic rays.

And radi­ation pro­tec­tion is just one of the many prob­lems that will have to be solved before send­ing humans to Mars. As for water, a lot of work has been done on the ISS and there is now a very effi­cient sys­tem that recycles urine and even recov­ers the water vapour emit­ted by breath­ing and per­spir­a­tion to fil­ter it and make drink­ing water. But even so, losses are inev­it­able, and the cargo ships that leave for the ISS every month always bring some water for refuelling.

As far as food is con­cerned, the prob­lem is far from being solved. It is impossible, for example, to carry 12 to 18 months’ worth of pro­vi­sions in a trail­er behind the space­craft (assum­ing that the crew is not aban­doned without the pos­sib­il­ity of return­ing, in which case the amount to be car­ried can be halved).

How­ever, there is still some research to find solu­tions on the ISS. Since 2019, the BioNutrients‑1 (then 2) exper­i­ment has been study­ing the func­tion­ing of cer­tain yeasts and bac­teria that have been genet­ic­ally mod­i­fied to pro­duce anti­ox­id­ants, vit­am­in A or pro­teins to main­tain the astro­nauts’ muscle mass. With the pro­gress of gene edit­ing, it is not unreal­ist­ic to ima­gine, in the long term, micro-organ­isms cap­able, for example, of break­ing down human fae­ces into simple molecules, and oth­ers pro­grammed to use this ele­ment­ary soup to pro­duce pro­teins, fats, fibres and oth­er con­sum­able car­bo­hydrates – and to be able to recycle, this time, some of the human sol­id matter.

Anoth­er well-known prob­lem of the space envir­on­ment on the human body is the decal­ci­fic­a­tion of bones. This phe­nomen­on can be slowed down by a suit­able diet and daily exer­cise, but this loss is inev­it­able (1% of bone mass lost per month). Here again, a solu­tion could come from bio­tech­no­logy. The idea is to use the veget­ables pro­duced inside the ves­sel in the most effi­cient and ver­sat­ile way pos­sible. In addi­tion to pro­du­cing a little oxy­gen by con­sum­ing CO₂ and serving as human food, it is also envis­aged that they could be used as a… pharmacy.

In space, astro­nauts lose 1% of their bone mass per month.

In 2022, a Uni­ver­sity of Cali­for­nia study was pub­lished on the growth in space of a genet­ic­ally mod­i­fied lettuce that pro­duces some human para­thyroid hor­mone, which, among oth­er things, helps stim­u­late bone growth. Daily con­sump­tion of this lettuce could even­tu­ally help astro­nauts main­tain their bone dens­ity dur­ing long space travel. We can then ima­gine hav­ing a pro­gram­mable plant phar­ma­co­poeia inside the space­craft, edited as needed, without hav­ing to take a whole phar­macy with us on take-off.

Finally, the human factor is also a very sens­it­ive para­met­er that does not neces­sar­ily guar­an­tee the suc­cess of a hypo­thet­ic­al mis­sion to Mars. A lot of research is cur­rently being car­ried out on the abil­ity of a small group of pseudo-astro­nauts to remain alone, liv­ing in promis­cu­ity 24 hours a day without the pos­sib­il­ity of chan­ging any­thing. But these stud­ies also have their lim­its because they take place in envir­on­ments that are cer­tainly isol­ated, but which remain on Earth. The know­ledge that there is no way back and that all of human­ity is behind you is impossible to simulate.

Few sci­ent­ists doubt that Mars is forever out of reach. But that does­n’t make the trip ready for tomor­row. Although intens­ive work is cur­rently being done to pre­pare man­kind for the first inter­plan­et­ary jour­neys, the cur­rent state of know­ledge and tech­no­logy for mak­ing this jour­ney cer­tainly does not make it pos­sible to envis­age it for the near future.