NASA’s Hubble Space Telescope spots Mars-bound comet sprout multiple jets

The observation of Comet Siding Spring (C/2013 A1) should allow astronomers to measure the direction of the nucleus' pole and axis of rotation.
By and | Published: March 28, 2014 | Last updated on May 18, 2023
Comet Siding Spring (C/2013 A1)
This is a series of Hubble Space Telescope pictures of Comet Siding Spring (C/2013 A1) as observed on October 29, 2013; January 21, 2014; and March 11, 2014. The distances from Earth were, respectively, 376 million miles (605 million kilometers), 343 million miles (552 million km), and 353 million miles (568 million km). The solid icy nucleus is too small to be resolved by Hubble, but it lies at the center of a dusty coma that is roughly 12,000 miles (19,000km) across in these images.
NASA/ESA/J.-Y. Li (Planetary Science Institute)
NASA has released an image of a comet that on October 19 will pass within 84,000 miles (135,000 kilometers) of Mars — less than half the distance between Earth and our Moon.

The image captured March 11 by NASA’s Hubble Space Telescope shows Comet Siding Spring (C/2013 A1) at a distance of 353 million miles (568 million km) from Earth. Hubble can’t see Siding Spring’s icy nucleus because of its diminutive size. The nucleus is surrounded by a glowing dust cloud, or coma, that measures roughly 12,000 miles (19,000km) across.

But after applying image-processing techniques to remove the hazy glow of the coma, scientists revealed what appear to be two jets of dust coming off the location of the nucleus in opposite directions. This observation should allow astronomers to measure the direction of the nucleus’ pole and axis of rotation.

Hubble also observed Siding Spring on January 21 as Earth was crossing its orbital plane, which is the path the comet takes as it orbits the Sun. This positioning of the two bodies allowed astronomers to determine the speed of the dust coming off the nucleus.

“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.

Discovered in January 2013 by Robert H. McNaught at Siding Spring Observatory, the comet is falling toward the Sun along a roughly 1-million-year orbit and is now within the radius of Jupiter’s orbit. The comet will make its closest approach to our star October 25, at a distance of 130 million miles (210 million km) — well outside Earth’s orbit. The comet is not expected to become bright enough to be visible with the naked eye.