After lurking in the outer reaches of the solar system for the past one million years, a comet is heading for a close encounter with Mars. The Hubble Space Telescope is keeping tabs on the icy interloper, seen in just-released images.
Comet C/2013 A1 (Siding Spring), which now lies some 353 million miles (568 million kilometers) from Earth, was discovered by Australia’s Robert McNaught, a prolific comet and asteroid hunter, more than a year ago. NASA’s Near-Earth Object Program Office at the Jet Propulsion Laboratory, in Pasadena, California, has been refining the comet’s exact trajectory ever since.
While researchers have ruled out a direct collision with Mars, the dusty coma of the comet (which is nearly as large as the entire Earth) will sweep directly across the red planet. The comet core, or nucleus, is expected make its closest approach to the red planet on October 19 at 2:28 p.m. ET. It will pass within 85,600 miles (137,760 kilometers) of Mars—less than half the distance from the Earth to the moon.
Hubble snapped these views of Siding Spring in late January and again on March 11 (photo above), just as our planet crossed the orbital path of the comet. That allowed astronomers to precisely clock the speeds of the dust flying off the comet’s icy nucleus.
With the comet particles blasting away from its surface at speeds of 125,000 miles per hour (56 kilometers per second), space agency officials are concerned about possible damage to spacecraft in orbit around the red planet.
“This is critical information that we need to determine whether, and to what degree, dust grains in the coma of the comet will impact Mars and spacecraft in the vicinity of Mars,” said Jian-Yang Li of the Planetary Science Institute in Tucson, Arizona.
At this moment in time, various mission teams are not sure exactly the level of risk they are dealing with, but they are preparing for all scenarios.
“Our plans for using spacecraft at Mars to observe comet Siding Spring will be coordinated with plans for how the orbiters will duck and cover, if we need to do that,” said Rich Zurek, Mars Exploration Program chief scientist at NASA’s Jet Propulsion Laboratory, in a statement in January.
How much threat Mars orbiters will face will really depend on how much dust is being thrown off by the comet, and in what direction the orbiters will be heading at the time of encounter.
Precautionary measures might include facing the orbiters away from the onslaught of the fast-moving particles, or making sure that the spacecraft are on the opposite side of Mars when they arrive—using the planet as a natural shield during the comet’s closest approach.
Meanwhile, the rovers on the surface are thought to be out of danger since the Martian atmosphere is thick enough to prevent the dust from doing any damage.
See for Yourself
By October 25 the comet will reach its closest approach to our planet, coming about 130 million miles (209 million kilometers) from the sun; however, it’s not expected to become visible to the naked eye.
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.
There is still hope that, starting around mid-September, Siding Spring may become visible in the evening skies through binoculars and backyard scopes for us Earthlings.
Quite a sky show might be seen from the surface of Mars through the electronic eyes of the Opportunity and Curiosity rovers looking up, as well.
Current brightness magnitudes indicate that the comet will be very bright to their digital eyes. Comet fans can hardly wait to see the picture postcards that will be beamed back from these intrepid robotic explorers. Stay tuned for more details!