Earth’s neighbor is once again making the news, but not for the usual reasons. Rather than groundbreaking discoveries or updates being provided by the small army of rovers or satellites, the NASA has now got its eyes firmly fixed on the Red Planet because of an incoming comet. And in the coming months, NASA is taking every precaution to make sure its orbiting spacecraft are out of the way.
Known as C/2013 A1 Siding Spring, the comet’s icy nucleus is predicted to flyby Mars on Oct. 19th, and will miss the planet by just 132,000 km (82,000 miles). That’s 17 times closer than the closest recorded Earth-approaching comet, Lexell’s Comet, which skittered by our world in 1770. And while this is certainly a record-breaking event, no one is concerned about it damaging anything on the Martian surface.
In fact, it the dust particles embedded in the comet’s vaporizing ice that concerns NASA planners. As dust spreads into a broad tail that could potentially brush Mars’ upper atmosphere, it could also play havoc with or even strike an orbiter. While tiny particles are hardly a hazard on their own, when they are traveling at 56 km (35 miles) per second relative to a spacecraft, a single impact could spell disaster.
Rich Zurek, chief scientist for the Mars Exploration Program at NASA’s Jet Propulsion Laboratory in Pasadena, California, explains:
Three expert teams have modeled this comet for NASA and provided forecasts for its flyby of Mars. The hazard is not an impact of the comet nucleus, but the trail of debris coming from it. Using constraints provided by Earth-based observations, the modeling results indicate that the hazard is not as great as first anticipated. Mars will be right at the edge of the debris cloud, so it might encounter some of the particles — or it might not.
Hence why NASA is looking to get its hardware out of the way. The agency currently operates the Mars Reconnaissance Orbiter (MRO) and Mars Odyssey spacecraft with a third orbiter, MAVEN, currently on its way to the planet and expected to settle into orbit a month before the comet flyby. Teams operating the orbiters plan to have all spacecraft positioned on the opposite side of Mars when the comet is most likely to pass by.
Already, mission planners tweaked MRO’s orbit on July 2 to move it toward a safe position with a second maneuver to follow on August 27. A similar adjustment is planned for Mars Odyssey on August 5 and October 9 for the Mars Atmosphere and Volatile Evolution (MAVEN) probe. The time of greatest risk to the spacecraft is brief – about 20 minutes – when the widest part of the comet’s tail passes closest to the planet.
As for the rovers on the surface, there really isn’t much to worry about there. Similar to what happens with meteor showers here on Earth, Mars’ atmosphere is thick enough that cometary dust particles will incinerate before they reach the surface. And its expected that rover cameras may be used to photograph the comet before the flyby and to capture meteors during the comet’s closest approach.
Despite concerns about dust, NASA knows a good opportunity when it sees one. In the days before and after the flyby, all three orbiters will conduct studies on the comet. According to a recent NASA press release, instruments on MRO and Odyssey will examine the nucleus, coma and tail and possible effects on the Martian atmosphere:
Odyssey will study thermal and spectral properties of the comet’s coma and tail. MRO will monitor Mars’ atmosphere for possible temperature increases and cloud formation, as well as changes in electron density at high altitudes and MAVEN will study gases coming off the comet’s nucleus as it’s warmed by the sun. The team anticipates this event will yield detailed views of the comet’s nucleus and potentially reveal its rotation rate and surface features.
This is Comet Siding Spring’s first trip to the inner solar system, so we can expect plenty of news and updates as it passes Mars. And the icy vapor and dust it leaves behind, which has been in a state of deep freeze since the time the planets were formed, will make for some pretty interest research as well! And be sure to check out this Solar System Scope simulation of the comet’s path as it makes it way through our Solar System past Mars.