As a Science honours student, Andy’s column ‘Next Week in the Future’ examines current issues in science and tech, to keep you informed for when these topics come up during conversation.
In the last minute of the Perseverance rover’s descent towards Mars on 18 February 2021, the ‘War Room’ at the Jet Propulsion Laboratory has an atmosphere of intense focus, but it swells with anticipation by the moment.
“Tango delta!” someone calls out. Phonetic code for the letters ‘TD’ – that’s NASA code for the first sign of touchdown. Cautious to a fault, a convention put in place for the 2012 Curiosity dictates that the word ‘touchdown’ is not said until safe touchdown is absolutely certain.
All is well — that moment comes seconds later as engineer Dr. Swati Mohan cuts the suspense: “Touchdown confirmed!”
The War Room leaps to its feet. Mohan announces, with audible jubilation: “Perseverance, safely on the surface of Mars, ready to begin seeking the signs of past life.”
Perseverance‘s safe landing in Jezero Crater concluded a seven month journey to Mars. Jezero — named after a Bosnian town whose name literally means ‘lake’ — is an ancient meteorite crater, about 50km in diameter, and containing rocks up to 3.6 billion years old. It’s believed that, around that time, the crater was fed by rivers of liquid water, forming a lake. Though any water present is long gone, it has left behind a delta — a fan-shaped clay deposit. And just as river deltas on Earth are rich with organic remains preserved by mud, Martian deltas are natural places to look for hints of past life.
Perseverance (affectionately nicknamed Percy) was based on NASA’s last rover, Curiosity, which landed in 2012. Although Percy and Curiosity look very similar, Percy is part of a wider space mission called Mars 2020. The equipment on board Percy and the goals of the Mars 2020 mission are testament to eight years of scientific advancement.
The mission Mars 2020 has four named objectives. Two of these — Objective A, Geology and Objective B, Astrobiology — are similar to Curiosity‘s areas of inquiry, but the parameters have changed massively. Curiosity‘s mission was to ‘search for geological clues’ to Mars’s past environment, particularly its water activity, and ‘assess whether those environments were conducive to life’. Perseverance won’t just look for evidence that Jezero was conducive to life — it will actively look for biosignatures (evidence of ancient life itself). Although fossils would be a dramatic find, biosignatures could include less exciting things like chemical or mineral evidence, such as the presence of limestone. On Earth, the majority of limestone formation is owed to biological processes.
Perseverance‘s objectives also show how much closer we are to a new stage in Mars exploration — return missions. While Curiosity collected samples exclusively to be analysed with its on-board instruments, Perseverance will collect samples that will be dropped on Mars to be retrieved by another mission down the line. This is Objective C: Sample Caching. Perseverance‘s drill, bigger and less destructive than Curiosity‘s, can extract intact cores of rock and deposit them in a sample container, to be later dropped at a sheltered location on Mars. In collaboration with the European Space Agency (ESA), NASA is exploring ways to get the samples back. Since Perseverance has no way of returning to space, this will require a new spacecraft to be launched to Mars.
NASA’s suggested timeline for Mars Sample Return (MSR) program outlines a 2026 launch, 2028 arrival on Mars, and 2031 return of samples to Earth. This seems especially ambitious, considering that NASA only officially entered development for a Mars sample return mission this year — indeed, an independent review board has recommended delaying launches to 2027-2028. The reward — the opportunity to analyse Martian material on Earth — will hopefully be worth the wait. And, although all parts of the mission will be automated, it will be an important proof-of-concept for human-crewed return missions even further down the line.
That’s the spirit of Perseverance‘s final goal: Objective D, Prepare for Humans. While building a self-sufficient rover is itself a vast challenge, a return mission — whether crewed or uncrewed — will have even greater resource demands. For example, a rocket crewed by just four people would require some 25 tonnes of oxygen propellant to escape the planet. Safely landing such a heavy payload, along with the rest of the spacecraft and crew, would be a feat — in comparison, Perseverance weighs just over 1 tonne.
Michael Hecht, of MIT, provides an answer to the dilemma: “Bring an empty oxygen tank and fill it up on Mars.” Hecht is the principal investigator for MOXIE, an oxygen generation experiment on board Perseverance. This car-battery-sized device captures atmospheric carbon dioxide (CO2) to convert it into oxygen (O2) with carbon monoxide (CO) as a by-product. MOXIE doesn’t make a lot (at most 10 grams of oxygen per hour), and Perseverance doesn’t actually need the oxygen (it gets vented back into the atmosphere), but it’s a valuable experiment for the future. According to NASA, a generator that is about 100 times larger could provide for the oxygen needs of a human mission to Mars. Surprisingly, the majority of that will be used as propellant, not for breathing. ‘Rockets breathe millions of times as much oxygen as people’, Hecht puts simply.
This is what Mars 2020 is about — more than just studying the planet, it’s about testing the technology for a human mission. And even the study of Mars has changed, as evidence for past habitability has become sufficient to justify an active search for signs of past life.
There is one little thing that doesn’t fit in these categories, but is already threatening to steal the show with its adorableness: Ingenuity, the Mars Helicopter that hitched a ride to Mars inside Percy. The tiny 1.8 kg rotocraft will hopefully make the first powered flight in the atmosphere of Mars. Although the low gravity means it weighs just 0.68 kg on Mars, its rotors will have to spin at between 2000 and 3000 rpm to achieve lift in the thin atmosphere. Ingenuity is yet to perform its first flight, which will be in April at the earliest — you can stay updated here.