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.