MOXIE, the technology on Perseverance that produced oxygen on Mars



by LORENZO CIOTTI

MOXIE, the technology on Perseverance that produced oxygen on Mars

Mars 2020 is a space mission for the exploration of Mars that was developed by NASA, whose launch took place successfully on 30 July 2020 and its arrival on the surface of Mars was equally successful on 18 February 2021. The mission is mainly focused on sending Perseverance to the surface of Mars, a rover derived from its predecessor Curiosity to reduce costs, to which several improvements have been applied.

In addition to the rover there is a small demonstration helicopter called Ingenuity. The primary objectives of the mission are to study the habitability of Mars, to investigate its past and to search for traces of possible biological life.

Furthermore, the storage of geological samples is planned to allow the future Mars Sample Return mission to bring them to Earth in order to analyze them accurately. The Mars 2020 mission is part of NASA's Mars Exploration Program, which includes, in addition to Curiosity, the two Mars Odyssey and Mars Reconnaissance Orbiter probes currently orbiting the planet, and the MAVEN orbiter which arrived on Mars in month of September 2016 and will study its upper atmosphere.

In May 2018, a lander called InSight was launched to give a first look into the planet's deep interior. The rover brings with it seven instruments chosen from a selection from 58 proposals, 23 cameras including: 9 so-called engineering, 7 scientific and a further 7 used for the descent and landing phase on Martian soil.

It is also equipped with two microphones to record ambient sound during the rover's descent, landing and operation on the ground. The overall mass amounts to approximately 29 kg while the maximum absorption is 436 W. The total cost of developing the scientific instrumentation amounts to approximately 130 million dollars.

The Moxie is an instrument for the scientific demonstration of the extraction, in local conditions, of oxygen (O2) from carbon dioxide (CO2) which almost exclusively makes up the Martian atmosphere. Moxie first stores and compresses CO2, then, through an electrolytic reaction, divides the CO2 molecules into O2 and carbon monoxide (CO).

The instrument is made up of three modules, the first is the CAC (The (CO2) Acquisition and Compression), i.e. the compressor, which sucks CO2 from the atmosphere and compresses it to ~ 1 atm. The pressurized gas is then supplied to the second module, the SOXE (Solid OXide Electrolyzer), i.e.

the module where the electrolytic reaction takes place: 2CO2 → O2 + 2CO where the O2 is produced at the anode, it is equivalent to the process of a fuel cell in reverse. The SOXE operates at a temperature of approximately 800 °C, therefore requiring sophisticated thermal protection, including pre-heating of the incoming gas and cooling of the outgoing gas.

The O2 output flow is separated from that of O2 and CO, this to allow better verification of the quantity of oxygen produced. Furthermore the current passing through the SOXE is a direct result of the oxide ions passing through the electrolyte and this provides an independent measurement of the rate of O2 production produced.

The measurement of the quantity of O2 output is measured by the third module. Everything is managed by electronics that collects the data and sends them towards Earth. The MOXIE weighs no more than 1.8 kg and has a power consumption of 300 W.