The Sun also emits atmosphere-busting ions, though predominantly ones with much lower mass. Based on the different masses of ions measured, STATIC determined which particles came from Mars rather than from the Sun. This allows scientists to compute their mass.
STATIC measures the kinetic energy and velocity of incoming particles. They relied on MAVEN’s Suprathermal and Thermal Ion Composition instrument, or STATIC, to measure the Martian ions in Phobos’ orbit. This visualization shows the MAVEN spacecraft's orbit change during its primary mission as it progressed from the initial, highly elliptical entry orbit to a somewhat less elliptical orbit, and finally to the science orbit. Since the spacecraft crossed the orbit of Phobos about five times each Earth day as it circled Mars during its primary mission, Nénon and his colleagues figured they could use MAVEN measurements to learn something about Phobos, especially since it is the target of the forthcoming MMX mission. MAVEN has been collecting data from the orbit of Mars for more than six years in order to help scientists figure out how Mars lost its atmosphere and to provide other important scientific insights on the evolution of the planet’s climate. Nénon’s team analyzed data from NASA’s Mars Atmosphere and Volatile EvolutioN, or MAVEN, spacecraft to reach this conclusion.
#AS DEVIOUS AS THE STONE FACE OF MARS WATCHES PHOBOS ARCHIVE#
“With a sample from the near side,” Nénon said, “we could see an archive of the past atmosphere of Mars in the shallow layers of grain, while deeper in the grain we could see the primitive composition of Phobos.” Nénon’s research shows that the uppermost surface layer of Phobos’ near side has been subjected to 20 to 100 times more wayward Martian ions than its far side. As a result, the rocks on the near side of Phobos have been bathed for millennia in Martian atoms and molecules. Phobos is tidally locked to Mars, like Earth’s moon is locked to Earth, thus always showing the planet only one side.
But those samples, Nénon noted, could reveal a lot more than the origin of Phobos if MMX were to land on the near side of the moon, or the side that always faces Mars. In order to help settle the debate, Japan Aerospace Exploration Agency is preparing to send the Martian Moons Exploration (MMX) probe to Phobos in 2024 to collect the first samples from its surface and deliver them to Earth. The mystery is where did Phobos and Deimos come from? Are they asteroids that were captured by Martian gravity, or natural satellites of Mars that were spawned by the same cloud that created the planet? It’s also possible that they formed from the debris that spewed when Mars collided with something, similar to how our Moon is thought to have formed after Earth collided with a rocky object. Misshapen, pockmarked by craters, and 100 times smaller in diameter than Earth’s moon, Phobos is the source of great controversy among scientists. It orbits intimately close to the Red Planet, about 60 times closer than the Moon orbits Earth, as measured from approximately surface to surface. Phobos is one of two moons of Mars (the other is called Deimos). Credits: NASA/JPL-Caltech/University of Arizona. Mars' Moon Phobos : The High Resolution Imaging Science Experiment (HiRISE) camera on NASA's Mars Reconnaissance Orbiter took two images of the larger of Mars' two moons, Phobos, within 10 minutes of each other on March 23, 2008. “We knew that Mars lost its atmosphere to space, and now we know that some of it ended up on Phobos,” said Quentin Nénon, a researcher at the Space Sciences Laboratory at the University of California, Berkeley, and the study’s lead author.
Mars once had an atmosphere thick enough to support liquid water on its surface today, it’s less than 1% as dense as Earth’s. This means that if soil from Phobos were analyzed in labs on Earth, it could reveal key information about the evolution of the Martian atmosphere, researchers say. Some ions, scientists predict, have been smashing into the surface of Phobos and could be preserved in its uppermost layer, according to a paper published on Feb. Many of these charged particles, or ions, of oxygen, carbon, nitrogen, and argon, have been escaping Mars for billions of years as the planet has been shedding its atmosphere. The Martian moon Phobos orbits through a stream of charged atoms and molecules that flow off the Red Planet’s atmosphere, new research shows.
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