Tag: Phobos. Deimos

Planetary Protection and the Moons of Mars

Mars with its two moons, Phobos and Deimos. Phobos orbits a mere 3,700 mile3s (6,000 km) above the surface, while Deimos is almost 15,000 miles (24,000 kilometers) away from the planet. In comparison, there is an almost 384,000 kilometers mean distance between the surface of the Earth and our elliptically orbiting moon. With the moons so close to Mars, debris from meteorite impacts on the planet can easily land on the moons. (NASA/JPL-Caltech/University of Arizona)

Sometime in the early to mid-2020s, the capsule of the Japanese Martian Moons eXploration (MMX) mission is scheduled to arrive at the moons of Mars – Phobos and Deimos.

These are small and desolate places, but one goal of the mission is large: to collect samples from the moons and bring them back to Earth.

If it succeeds, the return would likely be the first ever from Mars or its moons — since planned sample return efforts from the planet itself will be considerably more challenging and so will take longer to plan and carry out.

The Mars moon mission has the potential to bring back significant information about their host planet, the early days of our solar system, and the origins and make-up of the moons themselves.

It also has the potential, theoretically at least, to bring back Martian life, or signatures of past Martian microbial life. And similarly, it has the potential to bring Earth life to one of the moons.

Hidenori Genda, an ELSI planetary scientist with a long-lasting interest in the effects of giant planetary impacts, such as the one that formed our moon. His work has also focused on atmospheres, oceans, and life beyond Earth. (Nerissa Escanlar)

Under the general protocols of what is called “planetary protection,” this is a paramount issue and is why the Japan Aerospace Exploration Agency (JAXA) was obliged to assess the likelihood of any such biological transfers with MMX.

To make that assessment, the agency turned to a panel of experts that included planetary scientist, principal investigator, and associate professor Hidenori Genda of Tokyo’s Earth-Life Science Institute.

The panel’s report to JAXA and the journal Life Sciences in Space Research concluded that microbial biology (if it ever existed) on early Mars could have been kicked up by incoming meteorites, and subsequently traveled the relatively short distance through space to land on Phobos and Deimos.

However, the panel’s conclusions were unambiguous: the severe radiation these microbes would encounter on the way would make sure anything once living was now dead.… Read more

Japan’s Mission to the Martian Moons Will Return a Sample From Phobos. What Makes This Moon So Exciting?

Artist impression of JAXA’s MMX spacecraft around Mars (JAXA).

Japan in planning to launch a mission to visit the two moons of Mars in 2024. The spacecraft will touchdown on the surface of Phobos, gathering a sample to bring back to Earth. But what is so important about a moon the size of a city?

Unlike the spherical shape of the Earth’s moon, the Martian moons resemble asteroids, with an asymmetric lumpy potato structure. This highlights one of the first mysteries about the pair: how did they form?

Light reflected from the moons’ surface gives clues to their composition, as different minerals absorb particular wavelengths of radiation. If an object reflects more light at longer wavelengths, it is said to have a spectra with a red slope. This is true of both Phobos and Deimos, which appear very dark in visible light but reflect more strongly in longer near-infrared wavelengths. It is also true of D-type asteroids, which orbit the sun in the outer edge of the asteroid belt that sits between Mars and Jupiter.

The similarities between both their lumpy shape and reflected light has led to speculation that the two moons are captured asteroids, snagged by Mars’s gravity after a collision in the asteroid belt scattered them towards the sun.

How did the martian moons form? Were they asteroids captured by Mars’s gravity or formed during a giant impact event? (Elizabeth Tasker)

However, such a gravitational lasso would typically move the captured object onto an inclined or highly elliptical orbit. Neptune’s moon, Triton, is suspected to be captured as it orbits in the reverse direction to Neptune’s own spin and on a path tilted from the ice giant’s equator by 157 degrees.

Yet both Phobos and Deimos sit on near-circular orbits in the equatorial plane of the planet. This configuration suggests the moons may have been formed in a giant impact with Mars, which threw debris into orbit and this coalesced into the two moons.

This mystery will be one of the first tackled by Japan’s planned Martian Moons eXploration (MMX) mission, that is due to launch in the fiscal year of 2024. Onboard are multiple instruments designed to unpick the moons’ composition from close quarters, providing far more detailed information than that from distant reflected light.

If these moons are impact debris, their composition should be similar to Mars. Captured asteroids would show a more unique rocky formula.… Read more

Phobos and Deimos: Captured Asteroids or Cut From Ancient Mars?

Illustration of Mars with its two moons, Phobos and Deimos. (NASA/JPL-Caltech/Malin Space Science Systems/Texas A&M Univ.)

The global success rate for sending missions to land on the moons of Mars has hardly been impressive — coming in at zero out of three attempts.  They were all led by the Russian (or former Soviet) space agencies, in collaboration with organizations ranging from the Chinese and Bulgarian space agencies to the Paris Observatory and the U.S. Planetary Society.

Now the Japanese space agency JAXA has approved its own mission to Phobos and Deimos, scheduled to launch from the Tanegashima Space Center in September 2024.

The Martian Moons eXploration (MMX) spacecraft will arrive at Mars in August 2025 and spend the next three years exploring the two moons and the environment around Mars. During this time, the spacecraft will drop to the surface of one of the moons and collect a sample to bring back to Earth. Probe and sample are scheduled to return to Earth in the summer of 2029.

Mars takes its name from the god of war in ancient Greek and Roman mythology. The Greek god Ares became Mars in the Roman adaptation of the deities. Mars’s two moons are named for Phobos and Deimos; in legend the twin sons of Ares who personified fear and panic.

Today, what the moons together personify is a compelling mystery, one regarding how in reality they came to be.

Both Martian moons are small, with Phobos’s average diameter measuring 22.2km, while the even smaller Deimos has an average size of just 13km. This makes even Phobos’s surface area only comparable to that of Tokyo. Their diminutive proportions means that the moons resemble asteroids, with irregular structures due to their gravity being too weak to pull them into spheres.

This leads to the question that has inspired a long-running debate: Were Phobos and Deimos formed during an impact with Mars, or are they asteroids that have been captured by Mars’s gravity?

Phobos and Deimos, photographed by the Mars Reconnaissance Orbiter. (NASA/JPL)

Our own Moon is thought to have been created when a Mars-sized body slammed into the early Earth. Debris from the collision was thrown into the Earth’s orbit where is coalesced into our only natural satellite.

A similar scenario is possible for Phobos and Deimos. In the late stages of our solar system’s formation, giant impacts such as the one that struck the Earth were relatively common.… Read more

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