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MOXIE (Mars OXygen In situ resource utilization Experiment) is an exploration technology experiment that will produce oxygen from Martian atmospheric carbon dioxide (CO2) in a process called solid oxide electrolysis.
Contents
MOXIE is a 1% scale model aboard the planned Mars 2020 rover. The Principal Investigator of the MOXIE instrument is Michael Hecht from the Massachusetts Institute of Technology (MIT). The Niels Bohr Institute at the University of Copenhagen is collaborating with MIT to develop this prototype.
Objective
The main objective of this experiment is to produce oxygen on Mars, where the atmosphere is 96% carbon dioxide. Scientists will record the efficiency of the O2 production rate, and the resulting oxygen and carbon monoxide will be vented out after measurements are done.
To achieve this objective, the MOXIE instrument has a goal of producing 22 g of oxygen (O2) per hour with >99.6% purity during 50 sols (Martian days). High purity is crucial as future astronauts will breathe it.
NASA officials stated that if MOXIE worked efficiently, they would land a 100 times larger MOXIE-based instrument on Mars, along with a radioisotope thermoelectric generator. Over the course of some years the generator would power the system, which would produce up to two kilograms of oxygen per hour, and fill an oxygen reservoir that could be used when astronauts arrive sometime in the 2030s. The stored oxygen could be used for life support, and can also be used as rocket propellant oxidizer to power their return trip to Earth. The carbon monoxide (CO), a byproduct of the reaction, may also be collected and used directly as propellant or converted to methane (CH4) for use as propellant.
Background
The MOXIE experiment follows up on an earlier experiment, Mars ISPP Precursor ("MIP"), which was designed and built to fly on the Mars Surveyor 2001 Lander mission. MIP was intended to demonstrate In-Situ Propellant Production ("ISPP") at a laboratory-scale using electrolysis of carbon dioxide to produce oxygen on Mars. The MIP experiment was mothballed when the 2001 Lander mission was cancelled following the failure of the 1998 Mars Polar Lander.
Principle
A solid oxide electrolysis cell works on the principle that, at elevated temperatures, certain ceramic oxides, such as yttria-stabilized zirconia (YSZ) and doped ceria, become oxygen ion (O−2) conductors. A thin nonporous disk of YSZ (solid electrolyte) is sandwiched between two porous electrodes. For oxygen generation from carbon dioxide, CO2 diffuses through the porous electrode (cathode) and reaches the vicinity of the electrode-electrolyte boundary. Through a combination of thermal dissociation and electrocatalysis, an oxygen atom is liberated from the CO2 molecule and picks up two electrons from the cathode to become an oxygen ion (O−2). Via oxygen ion vacancies in the crystal lattice of the electrolyte, the oxygen ion is transported to the electrolyte-anode interface due to the applied DC potential. At this interface the oxygen ion transfers its charge to the anode, combines with another oxygen atom to form oxygen (O2), and diffuses out of the anode. The net reaction is shown below: