A cometary near miss for Mars in a few months means meteor risks for NASA’s spacecraft orbiting the red planet.
On October 19, the comet Siding Spring will brush by Mars, passing so close that the space agency this week announced it has put together a special playbook filled with protective measures for its orbiters there.
While astronomers have ruled out a direct hit on the planet, the comet’s dusty coma (a cloud nearly as large as the Earth) will sweep directly across Mars, with the comet core buzzing within 85,600 miles (137,760 kilometers) of its surface—less than half the distance from the Earth to the moon.
Unlike NASA’s Mars rovers Curiosity and Opportunity, which will be perfectly safe and have amazing ringside seats to the sky show, the orbiters may be at risk of damage from a barrage of bullet-like cometary bits. Tiny dust particles traveling 125,200 miles per hour (201,490 kilometers per hour) could effectively sandblast the Mars spacecraft.
At this point NASA has Mars Odyssey and the Mars Reconnaissance Orbiter circling the red planet, along with Mars Express, a joint mission with the European Space Agency. By the end of September a fourth orbiting probe will reach the red planet, the Mars Atmosphere and Volatile Evolution or MAVEN.
Computer simulations of the comet’s swing around Mars show that about 90 minutes after its closest approach to the planet, there is a specific 20-minute window that poses the most danger to the orbiters from the comet’s debris trail. So NASA plans to use the planet as a shield for its probes during those critical minutes, just in case.
But the orbiters won’t be shying away from this cosmic show—NASA hopes to be able to capture some amazing science in the hours and days before and after the comet’s closest approach.
Scientists believe that this comet has never entered the inner solar system before. If true, that means the comet is a pristine remnant of the solar system’s early formation. By directly taking a taste and sniff of the icy visitor, we may actually be able to collect data that harken back to the birth of the planets, including the Earth.
See for Yourself
By October 25, the comet will reach its point of closest approach to Earth, coming about 130 million miles (209 million kilometers) from the sun. But even then it’s not expected to be visible to the naked eye.
Instead, it’s a safe bet that both backyard and professional stargazers will be training their telescopes on the red planet on October 19, hoping to get a good view of the cosmic near-miss. Mars will be low in the southwest sky, near the constellation Sagittarius, at that time.
There is still hope that, starting around mid-September, Siding Spring may become visible in the evening skies through binoculars and backyard scopes for those in the Southern Hemisphere. The comet will then be gliding through the constellation Ophiuchus, in the southwestern sky at dusk.