The UAE’s Hope probe has revealed striking details of Mars’s tiny moon Deimos, helping to indicate that the celestial body may not actually be a captured asteroid as previously thought.
The spacecraft flew as close as 100km to the moon’s surface, capturing data of its composition that challenges a long-standing theory that Mars’ moons are captured asteroids — space rocks trapped in a planet’s orbit.
Findings point to a planetary origin, meaning that the rock may have come from Mars itself.
“We are unsure of the origins of both Phobos [the larger moon of Mars] and Deimos,” Hessa Al Matroushi, the science lead of the mission, said.
“How exactly they came to be in their current orbits is also an active area of study, and so any new information we can gain on the two moons, especially the more rarely observed Deimos, has the potential to unlock new understanding of Mars’s satellites.
“Our close observations of Deimos so far point to a planetary origin rather than reflecting the composition of a type D asteroid as has been postulated.”
Deimos seen like never before
The Hope probe has spent the past two years studying the Red Planet from an elliptical orbit, a placement that helps the spacecraft “see” Mars from a relatively short distance, but also from much higher above.
It changed its orbit slightly in January to begin observations of both Mars and Deimos.
Since then, it has performed fly-bys that brought it as close as 100km to the surface of the moon's far side — the part of the rock that faces outward from Mars and remains largely unexplored.
Only Nasa's Viking mission in 1977 has got that close before.
Sarah Al Amiri, Minister of State for Public Education and Future Technology and chairwoman of the UAE Space Agency, told The National that only a few images of Deimos exist.
“Phobos is better mapped as the larger moon and also the one that's observed from the surface of Mars itself,” she said.
“The level we reached is up to 100 kilometres from the surface of Deimos, which is considered quite close to be able to map it.
“Mapping it using other wavelengths and instrumentation makes this significant from a science perspective.
“So, it's not only a beautiful image and the far side captured, but a bit of insight into the make-up of the moon itself as well.”
What do we already know about Deimos?
The side of Deimos facing Mars has been studied the most before, by rovers on the surface of the planet and orbiters.
This is because most Mars missions have operated in orbits much lower than Deimos.
The Hope probe has an advantage because it almost slingshots around the planet, with a current orbit of 20,000-43,000km and an inclination to Mars of 25°.
The Mariner 9 and Viking missions in the 1970s, and India's Mars Orbiter Mission in 2014, have captured images of the far side of Deimos, but not in as great detail as the latest images by the Hope spacecraft.
Other recent missions such as the Mars Reconnaissance Orbiter, Mars Odyssey and Mars Global Surveyor could only see half of the moon.
But what all observations were able to reveal is the odd shape of the moon and how its surface is much smoother than that of its companion Phobos.
What the Hope probe has discovered
Hope's observations reveal new details of the moon's surface composition, which could help scientists uncover its geological history.
“We have a unique opportunity with Hope to characterise the composition, thermophysics and detailed geomorphology of Deimos with these new observations,” Justin Deighan, the mission's deputy science lead, said.
“We expect to build a better understanding of both Phobos and Deimos’ origins and evolution and advance our fundamental understanding of these two satellites of Mars.”
The spacecraft's infrared spectrometre instrument has captured spectral data of nearly the entire surface of Deimos.
The data reveals the surface temperature variation, describe the surface physical properties and reveal the composition of the moon.
Findings show that Deimos' surface is not perfectly homogenous, but does likely have a fine-grained regolith and roughness.
Its surface also has similarities to Phobos’ and suggest a basaltic origin for the body.
These results support the interpretation that Deimos may be formed of coalesced pieces of Mars possibly ejected from a large impact rather than a captured carbonaceous D-Type asteroid.
Hope's mission extended by a year
The Hope spacecraft was launched to space in July 2020 and entered the orbit of Mars in February 2021.
Since then, it has been sending back crucial data on the planet's upper atmospheric conditions and space weather.
It tracked a massive dust storm on Mars for more than two weeks, helping to show how quickly they can spread across the planet.
It also captured rare images of the discrete aurora in Mars’s night-side atmosphere.
The findings help scientists understand the interactions between solar radiation, Mars’s magnetic fields and the atmosphere.
Ms Al Amiri said the Hope mission has now been extended for one more year because the “data is valuable”.
“Characterising the atmosphere, the spacecraft is ideally located and the data that's coming out of the mission will allow the observations to continue on into another year to give us more in-depth and details into that,” she said.
She said the team is expanding the number of partnerships with universities and researchers across the UAE to help maximise the scientific outcome of the mission.
The data so far has helped planetary scientists across the world in their research, including findings that are being used in many peer-reviewed science journals.