NASA Mars Moon Missions: Origins Investigation
Yes, NASA is sending new technology to Mars’s moons—Phobos and Deimos—to investigate their mysterious origins, specifically through the Martian Moons eXploration (MMX) mission led by JAXA (Japan Aerospace Exploration Agency) with significant NASA contributions. The mission aims to determine whether these small, irregular moons are captured asteroids, formed from a giant impact with Mars, or something else entirely.
Why the Moons of Mars Are So Mysterious
Phobos and Deimos are tiny, lumpy worlds—Phobos is about 22.5 km across, Deimos about 12.4 km—and they look more like dark, cratered potatoes than the round moons we’re used to. Their surfaces are covered in a thick layer of regolith (loose dust and rock), and their spectra resemble certain carbonaceous (C-type) asteroids. This led to the long-standing ‘captured asteroid’ theory: the idea that Mars’s gravity snagged them from the nearby asteroid belt. But there are problems with that idea. The moons’ orbits are nearly circular and lie almost exactly in Mars’s equatorial plane—a very precise alignment that is unlikely if they were randomly captured. Another theory suggests a giant impact on early Mars blasted material into orbit, which then coalesced into the two moons, similar to how our own Moon is thought to have formed. A third hybrid theory proposes that an asteroid was disrupted by Mars’s gravity, and the debris re-accreted into a disk that formed the moons. Each theory predicts different internal structures and compositions, which is exactly what MMX will test.
What New Technology Is NASA Sending?
NASA is contributing two key instruments to the MMX mission:
- MEGANE (Mars-moon Exploration with GAmma rays and NEutrons): This instrument measures gamma rays and neutrons emitted from Phobos’s surface. By analyzing their energies, scientists can determine the elemental composition of the top meter of the moon’s surface. This will tell us whether the material matches known asteroid types or is more like Mars’s own crust.
- IDEFIX (a rover): This small rover, developed by the German Aerospace Center (DLR) with NASA participation, will be deployed onto Phobos’s surface. It carries a gamma-ray spectrometer (also called MEGANE-like) and a radiometer to measure surface temperatures. The rover will move around using two wheels and a hopping mechanism, because Phobos’s gravity is so weak that a traditional rover might bounce off.
These instruments are ‘new technology’ in the sense that they are specifically designed to operate in the extremely low-gravity, dusty environment of a small moon, and they will provide the first direct compositional data from Phobos’s surface.
How the Mission Works: From Orbit to Sample Return
MMX is not just an orbiter; it’s a sample-return mission. The spacecraft will travel to Mars, enter orbit around Phobos, and perform detailed remote sensing over several months. Then it will attempt a landing on Phobos’s surface to collect a sample of regolith—at least 10 grams. This is a challenging operation because Phobos’s gravity is so weak that the spacecraft must use a touch-and-go technique, firing thrusters to stay attached during the brief contact. After collecting the sample, MMX will return it to Earth, where it will be studied in laboratories for decades. This will be the first sample ever returned from a Martian moon (and only the second from the Mars system after Mars 2020’s samples, which are still awaiting return). The mission is scheduled to launch in 2026 and return samples in 2031.
What Scientists Hope to Find in the Samples
The returned sample will be the ultimate arbiter of the moons’ origin. If the sample’s oxygen isotope ratios (a fingerprint of a body’s birth location) match Mars’s, that strongly supports the giant-impact theory. If they match certain carbonaceous asteroids, the captured-asteroid theory becomes more likely. The sample will also contain clues about the early solar system, as Phobos’s surface is likely ancient and unmodified by geological activity. Additionally, scientists will look for organic molecules and water-bearing minerals, which could tell us about the delivery of volatiles to the inner planets. The sample could also help calibrate remote-sensing data from other missions, improving our ability to interpret data from asteroids and other small bodies.
Challenges and Risks of Exploring Phobos
Phobos is a hostile environment. Its gravity is about 1/1000th of Earth’s, so any lander must be extremely careful not to bounce off. The surface is covered in dust that could cling to instruments and solar panels, and the temperature swings are extreme—from about -4°C in sunlight to -112°C in shadow. The moon is also tidally locked to Mars, so the same side always faces the planet, but the far side is in darkness for long periods. The mission must also deal with the fact that Phobos orbits Mars in just 7.6 hours, so the spacecraft’s orbital dynamics are complex. Despite these challenges, the scientific payoff is enormous, and the technology developed for MMX will be useful for future missions to other small bodies.
Frequently Asked Questions
Why are Phobos and Deimos not round like our Moon?
They are too small to have enough gravity to pull themselves into a sphere. The threshold for a body to become round (hydrostatic equilibrium) is roughly a few hundred kilometers in diameter, and both moons are far below that. So they retain irregular, potato-like shapes.
Could Phobos and Deimos be hollow or artificial?
No. There is no credible evidence for that. Their low densities (about 1.9 g/cm³ for Phobos) suggest they are porous, rubble-pile-like bodies, but that is consistent with natural formation processes. The ‘hollow’ idea comes from science fiction, not observation.
Will the sample return be dangerous to Earth?
No. The sample will be handled under strict planetary protection protocols, similar to the Apollo lunar samples and the Hayabusa asteroid samples. The material is likely sterile, but it will be treated as potentially hazardous until proven otherwise, and it will be kept in a secure curation facility.
How does MMX differ from previous Mars missions?
Previous missions like the Mars rovers and orbiters focused on Mars itself. MMX is the first mission dedicated to studying the moons in detail, and it’s the first to return a sample from them. It also carries a rover, which is new for a small-body mission.
When will we know the results?
The remote sensing data will start coming in shortly after arrival at Mars (expected in 2027), but the definitive answer will come from laboratory analysis of the returned sample, which is expected to reach Earth in 2031. That analysis could take years, so a full answer might not be available until the mid-2030s.
What if the sample doesn’t match either theory?
That would be exciting! It would mean our models of solar system formation need revision. For example, the sample could reveal that the moons are made of material from a different part of the solar system that migrated inward. Any unexpected result would open new avenues of research.
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