NASA Perseverance Rover's MOXIE Instrument On Mars Reliably Produces Oxygen: Study

NASA Perseverance MOXIE: Since April 2021, MOXIE has been generating oxygen from the Red Planet's carbon-dioxide-rich atmosphere. MOXIE recently completed its 11th run, its most productive run so far.

NASA Perseverance rover's lunch box-sized instrument 'MOXIE' is reliably producing oxygen on Mars, a new study reports. MOXIE, which stands for Mars Oxygen In-Situ Resource Utilization Equipment, is the first demonstration of in-situ resource utilisation on another planet. 

The Perseverance rover, launched as part of the Mars 2020 mission, landed on the Red Planet in February 2021. About two months after touching down on the Martian surface, MOXIE started generating oxygen from the Red Planet's carbon-dioxide-rich atmosphere. The instrument is performing the work of a small tree. 

The peer-reviewed study describing the findings was recently published in the journal Science Advances. In the study, scientists report that, by the end of 2021, MOXIE was able to produce oxygen on seven experimental runs, in a variety of atmospheric conditions. 

According to NASA, MOXIE recently completed its 11th run. This run turned out to be the most productive MOXIE run to date. 

What Is MOXIE? How Does It Demonstrate In-Situ Resource Utilisation?

In-situ resource utilisation (ISRU) is the term commonly used to describe the harvesting and processing of native resources on other planetary bodies, the study states. The idea behind the technology is to produce resources such as oxygen, which would otherwise have to be transported from Earth. MOXIE, which represents the first demonstration of ISRU technology on another planet, has been successfully producing oxygen from carbon-dioxide, which comprises 95 per cent of the Martian atmosphere. 

Between landing in February 2021 and the end of 2021, MOXIE has produced oxygen seven times. The instrument will continue to demonstrate oxygen production during night and day throughout all Martian seasons. 

What Can A Scaled-Up MOXIE Achieve?

A scaled-up MOXIE can produce tens of thousands of oxygen on-site. This enormous amount of oxygen is required for a rocket to transport astronauts off the surface of Mars. By producing tens of thousands of oxygen on the surface of Mars, MOXIE will eradicate the need to transport this huge quantity of oxygen from Earth to the Red Planet. 

According to the study, MOXIE reached its target of producing six grams of oxygen per hour, in each run. This is equivalent to the rate of oxygen production by a modest tree on Earth. A scaled-up version of MOXIE could continuously produce oxygen at the rate of several hundred trees. The oxygen generated would be enough to sustain humans once they arrive on Mars, and also to fuel a rocket for returning them to Earth. 

According to researchers, MOXIE's steady output of oxygen is a promising first step toward the goal. 

In a statement released by the Massachusetts Institute of Technology (MIT), which leads the experiment, Michael Hecht, principal investigator of the MOXIE mission at MIT's Haystack Observatory, said researchers have learned a tremendous amount that will inform future systems at a larger scale. A version of MOXIE scaled up to several hundred times can produce about two to three kilograms of oxygen per hour. 

MOXIE deputy principal investigator Jeffrey Hoffman said this is the first demonstration of actually using resources on the surface of another planetary body, and transforming them chemically into something that would be useful for a human mission. He called MOXIE's achievement "historic". 

Another potential native source for the manufacture of fuel and oxidiser on Mars is water ice. 

How Does MOXIE Generate Oxygen On Mars?

MOXIE is designed to run for short periods. The instrument starts up and shuts down with each run, depending on Perseverance's exploration schedule and mission responsibilities. These compromises in MOXIE's design were necessary for the instrument to fit aboard the rover. 

Despite these compromises, MOXIE has shown it can reliably and efficiently convert the carbon-dioxide from Mars' atmosphere into pure oxygen. MOXIE first draws the Martian air in through a filter that cleans it of contaminants. It is a dust-trapping HEPA (high-efficiency particulate air) filter.

Then, MOXIE compresses the atmosphere through a scroll pump, heats it to 800 degrees Celsius, and sends the air through an assembly, known as the solid oxide electrolysis (SOXE) assembly. 

Inside this assembly, carbon-dioxide flows over a cathode (a positive electrode that attracts electrons) and decomposes into oxygen ions and carbon-monoxide. 

After this, the oxygen ions are isolated. An electrolyte passes the oxygen ions to the anode (negative electrode). The oxygen ions are recombined to form breathable, molecular oxygen, or O₂. MOXIE measures the molecular oxygen for quantity and purity before releasing it into the Martian atmosphere. According to the study, the exhaust released from the cathode is a mixture of carbon-monoxide, carbon-dioxide, and inert atmospheric gases such as argon and nitrogen. 

MOXIE Has Produced Oxygen At Different Times Of Martian Year

Since the landing of the Perseverance rover on Mars in February 2021, MOXIE engineers have started up the instrument several times throughout the Martian year. Every time, it took the instrument a few hours to warm, and another hour to make oxygen before powering back down. In order to assess whether MOXIE could accommodate shifts in Mars' atmospheric conditions, engineers scheduled each run for a different time of day or night, and in different seasons. 

Hoffman said the atmosphere is far more variable than Earth, and that the density of the air can vary by a factor of two throughout the year. The temperature of the Martian air can vary by 100 degrees. 

Hoffman explained that one objective is to show that MOXIE can be run in all seasons. 

So far, the instrument has shown that it can produce oxygen at almost any time of the Martian day and year. 

Hecht said that the only thing MOXIE engineers have not demonstrated is running at dawn or dusk, when the temperature is changing substantially. He stated that engineers will first test this in the lab, and then try to achieve the milestone on the Red Planet. 

Why Can MOXIE Not Be Run Continuously?

MOXIE engineers will also monitor the system of the instrument for signs of wear and tear. The reason MOXIE cannot run continuously as a full-scale system would is that there are several other experiments aboard Perseverance. 

MOXIE must start up and shut down with each run. This is because thermal stress can degrade the system over time. 

What Is Special About MOXIE’s Latest Run?

MOXIE performed its 11th run during the peak of the Martian winter. This is the time when cold nights and relatively high atmospheric pressures conspire to produce the highest Martian air density of the year. The denser the air, the more carbon-dioxide MOXIE has to work with, and the more oxygen it can make.

Engineers are always extremely cautious about designing runs for the irreplaceable flight model on Mars. However, for MOXIE's 11th run, they pushed the envelope a little to briefly produce oxygen at a rate of nearly 10.5 grams per hour. If one doubles this amount, a human being could survive on it. This was a record for MOXIE. 

What Is Next For MOXIE?

MOXIE is reliably churning out oxygen on Mars. Now, engineers plan to push MOXIE's capacity, and increase its production, particularly in the Martian spring, according to MIT. This is because, in the Martian spring, the atmospheric density and carbon-dioxide levels are high.

Hecht said that the next run coming up will be during the highest density of the year, and MIT engineers just want to make as much oxygen as they can. He added that the engineers will set everything as high as they dare, and let MOXIE run as long as they can. 

Hoffman said that to support a human mission to Mars, one has to bring a lot of stuff from Earth, like computers, spacesuits, and habitats. But if one is able to make oxygen there, they are "way ahead of the game", he said. 

According to NASA, there is a long way to go before being able to produce two to three kilograms of oxygen per hour. This is the amount of oxygen that will be needed to make the tens of thousands of tonnes of propellant to lift a human crew of four to six astronauts off the surface of Mars and into Earth orbit.

This is the main objective of future oxygen generation technology to succeed MOXIE. However, this technology will require 25 kilowatts of power. MOXIE is able to utilise 100 watts of power. 

Scientists are testing ways to make the next MOXIE more power efficient. Right now, engineers use only about 10 per cent of MOXIE's power to generate oxygen. The rest of the power is utilised to run the compressor that collects the air, to operate the electronics, and to make up for heat loss from the electrolysis unit through the wires and tubes. 

According to NASA, scientists expect to use 90 per cent of the power in the full-scale version. They will make a few simple changes, like running the compressor at lower pressure and designing a more efficient oven.