Comet Siding Spring


Siding Spring MROThese images were taken of Comet C/2013 A1 Siding Spring by the Mars Reconnaissance Orbiter on 19 October during the comet’s close flyby of Mars. The comet is on its first trip this close to the sun from the Oort Cloud at the outer fringe of the Solar System. These are the first resolved images of the nucleus of a long-period comet.

The images of the comet were acquired at a range of about 138,000 kilometers. The scale is roughly 138 meters per pixel. Telescopic observations had suggested that the size of the nucleus was about 1 km wide. However, the best Mars Reconnaissance Orbiter images are two to three pixels across the brightest feature, suggesting that the size of the nucleus is less than half the earlier estimate.

This composite image shows two versions of two of the best images take by the HiRISE camera on the Mars Reconnaissance Orbiter. At the top are images with the full dynamic range, showing the nucleus and bright coma near the nucleus. At the bottom are versions where the fainter outer coma is brightened, saturating the inner region. The left and right images were taken about nine minutes apart.

Image Credit: NASA

Mars Orbiter and Comet Siding Spring


This afternoon, Comet C/2013 A1 (AKA Comet Siding Spring) will pass within about 140,000 km of Mars. That’s less than half the distance between Earth and the Moon and less than one-tenth the distance of any known comet flyby of Earth. Siding Spring’s nucleus will come closest to Mars around 18:27 UTC (2:27 pm ET) moving at around 56 km/s.

Video Credit: NASA

A Near Miss at Mars


Near MissThis graphic shows the predicted orbit of comet C/2013 A1 Siding Spring as it swings around the inner Solar System in 2014. On 19 October, the comet will pass very close to Mars. Its nucleus will miss Mars by about 132,000 km. As it flies by it, will be shedding material moving at over 50 km/s, relative to Mars and Mars-orbiting spacecraft. Even a tiny particle only 0.5 mm across moving at that speed could cause significant damage to a spacecraft.

NASA currently operates two Mars orbiters, and a third on its way, arriving in Martian orbit a month before the comet flyby. Teams operating those orbiters plan to adjust their orbits so that the spacecraft will be on the opposite side of the Mars when the comet is most likely to pass by.

Image Credit: NASA

Comet Siding Spring


Siding SpringThis is a composite of a series of images of Comet Siding Spring taken by the UV Optical Telescope aboard the Swift satellite during the last week of May.

The comet will make a close approach to Mars on 19 October, passing about 138,000 km from the planet. That’s should be close enough that gas and dust in the outermost reaches of the comet’s atmosphere, or coma, will interact with the atmosphere of Mars.

The closest recorded Earth approach by a comet was by the now-defunct comet Lexell. In 1770, it came within 2.3 million km. That’s roughly 6X the distance from the Earth to the Moon.

Image Credit: NASA

Comet Siding Spring


Siding SpringThis is a composite of a series of images of Comet Siding Spring taken by the UV Optical Telescope aboard the Swift satellite during the last week of May.

The comet will make a close approach to Mars on 19 October, passing about 138,000 km from the planet. That’s should be close enough that gas and dust in the outermost reaches of the comet’s atmosphere, or coma, will interact with the atmosphere of Mars.

The closest recorded Earth approach by a comet was by the now-defunct comet Lexell. In 1770, it came within 2.3 million km. That’s roughly 6X the distance from the Earth to the Moon.

Image Credit: NASA