Martian moons may have formed from a planetary impact

The origin of Mars' two small moons, Phobos and Deimos, has long been a mystery, with scientists debating whether they are captured asteroids or formed from debris after a planetary impact. A new study using data from the Mars Global Surveyor mission suggests the latter theory may be more accurate.

The study, published in the Journal of Geophysical Research: Planets, reanalyzed 20-year-old data and found that the composition of Phobos may be more similar to the Martian crust than previously thought. This finding supports the hypothesis that the moons formed from material ejected into orbit after a large impact on Mars.

Tim Glotch, a geoscientist at Stony Brook University and the study's lead author, said the research involved examining Phobos' heat signature in the mid-infrared range, which provided new insights into its composition. The data suggested that Phobos does not match the spectral characteristics of D-class asteroids, which are dark and carbon-rich, leading researchers to reconsider its origin.

Marc Fries, a planetary scientist at NASA, noted that the debate over the moons' origins has persisted for decades, with two competing theories—capture from the asteroid belt or formation from a planetary impact—both having strong arguments. While the new study does not provide a definitive answer, it adds valuable data to the ongoing discussion.

Glotch and his team compared Phobos' mid-infrared spectrum to meteorite samples, including one from the Tagish Lake meteorite, which some believe is related to D-class asteroids. Their findings showed that the meteorite did not match Phobos' heat signature, further supporting the idea that the moons may have originated from Mars itself.