Mars could face twice as many close encounters with potentially dangerous asteroids as Earth, according to a new study. This could jeopardize research missions on the Red Planet, but also provide insight into how the inner solar system was formed.
Asteroids pose the greatest threat to our planet from space — the 2013 Chelyabinsk meteor, for example, generated shock waves that injured more than 1,000 people and caused more than $33 million in infrastructure damage.
Astronomers and citizen asteroid hunters have discovered about 33,000 similar space rocks that whiz past Earth during their orbits around the Sun. Some of them are huge—more than 460 feet (140 meters) in diameter—and spin on paths that approach Earth’s orbit at a distance of less than 0.05 astronomical units (AU). (For reference, 1 AU is about 93 million miles, or 150 million kilometers ― the average distance between Earth and the Sun.) Tracking such potentially hazardous asteroids (PHAs) is a key component of planetary defense programs.
Neighboring Mars should be worse, since it’s right next to the main belt – a stretch of planetless rocky waste between the orbits of Mars and Jupiter. But it is not clear exactly how many asteroids fly past Mars. That could be a problem, study co-author Yufan Fane Zhou, a doctoral student in astronomy at Nanjing University in China, told Live Science in an email; Mars is host to many current missions and may one day be home to human colonies.
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To test whether humans on the Red Planet would be more at risk from potentially devastating impacts, Zhou and colleagues at Nanjing University analyzed how many asteroids approach Mars. They called these space rocks «CAPHA,» an acronym for «potentially hazardous near-approach asteroids.»
To determine the number of Mars CAPHAs, the team used computer models to simulate the motions of all eight planets and about 11,000 randomly selected asteroids over 100 million years. All of these asteroids started out in the main belt. Then, by looking at each asteroid’s proximity to six known voids — asteroid-poor zones within the main belt where runaway rocks could potentially slip out — the team classified about 10,000 asteroids as «near void.»
During the simulations, the researchers forced asteroids near the gap to move away from or towards the sun. This movement is due to the Yarkovsky effect, a force created when the sunlit surfaces of asteroids re-radiate the energy they receive, acting like mini-thrusters. Simulating this displacement is critical because over millennia it causes asteroids near the void to meander into the voids. Once there, the occasional gravitational tugs of Jupiter or Saturn distort the trajectories of these asteroids, sending them on potential collision courses with the inner planets.
The simulations revealed that every Earth year, about 52 large asteroids wander dangerously close to Mars — about 2.6 times the 20 or so that come close to Earth each year. Although these asteroids come closer to Mars than Earth’s CAPHA does to our planet, they also travel more slowly.
NASA missions may have already witnessed the effects of some of these asteroids colliding with Mars; a meteorite impact on December 24, 2021 caused a magnitude 4 earthquake that was captured by NASA’s Mars InSight lander.
Although Zhou was ambivalent about whether objects near Mars could affect current missions, he noted that in the future, «as human visits to Mars become more frequent, the threat posed by Mars-CAPHAs may be taken more seriously.»
However, Mars-CAPHA can also be informative for astronomers. «Asteroids around Mars can also deepen our understanding of the Martian environment, the interaction between asteroids and planets, and the evolutionary history of the inner solar system,» Zhou said. In fact, Zhou and colleagues suggest that at least two of these CAPHAs may even be visible from Earth in early 2025, when Mars will lie in line with Earth while orbiting on the same side of the Sun.
The research was published online May 9 in the journal Monthly Notices of the Royal Astronomical Society: Letters.
Originally Published at LiveScience.com.