NASA Spacecraft Sees Cosmic Snow Storm During Comet Encounter

PASADENA, Calif. — The EPOXI mission’s recent encounter with comet Hartley 2 provided the first images clear enough for scientists to link jets of dust and gas with specific surface features. NASA and other scientists have begun to analyze the images.

The EPOXI mission spacecraft revealed a cometary snow storm created by carbon dioxide jets spewing out tons of golf-ball to basketball-sized fluffy ice particles from the peanut-shaped comet’s rocky ends. At the same time, a different process was causing water vapor to escape from the comet’s smooth mid-section. This information sheds new light on the nature of comets and even planets.

This image from the High-Resolution Instrument on NASA's EPOXI mission spacecraft shows part of the nucleus of comet Hartley 2. Image Credit: NASA/JPL-Caltech/UMD

Scientists compared the new data to data from a comet the spacecraft previously visited that was somewhat different from Hartley 2. In 2005, the spacecraft successfully released an impactor into the path of comet Tempel 1, while observing it during a flyby.

“This is the first time we’ve ever seen individual chunks of ice in the cloud around a comet or jets definitively powered by carbon dioxide gas,” said Michael A’Hearn, principal investigator for the spacecraft at the University of Maryland. “We looked for, but didn’t see, such ice particles around comet Tempel 1.”

The new findings show Hartley 2 acts differently than Tempel 1 or the three other comets with nuclei imaged by spacecraft. Carbon dioxide appears to be a key to understanding Hartley 2 and explains why the smooth and rough areas scientists saw respond differently to solar heating, and have different mechanisms by which water escapes from the comet’s interior.

This image shows the nuclei of comets Tempel 1 and Hartley 2. Image credit: NASA/JPL-Caltech/UMD

“When we first saw all the specks surrounding the nucleus, our mouths dropped,” said Pete Schultz, EPOXI mission co-investigator at Brown University. “Stereo images reveal there are snowballs in front and behind the nucleus, making it look like a scene in one of those crystal snow globes.”

Data show the smooth area of comet Hartley 2 looks and behaves like most of the surface of comet Tempel 1, with water evaporating below the surface and percolating out through the dust. However, the rough areas of Hartley 2, with carbon dioxide jets spraying out ice particles, are very different.

“The carbon dioxide jets blast out water ice from specific locations in the rough areas resulting in a cloud of ice and snow,” said Jessica Sunshine, EPOXI deputy principal investigator at the University of Maryland. “Underneath the smooth middle area, water ice turns into water vapor that flows through the porous material, with the result that close to the comet in this area we see a lot of water vapor.”

Engineers at NASA’s Jet Propulsion Laboratory in Pasadena, Calif., have been looking for signs ice particles peppered the spacecraft. So far they found nine times when particles, estimated to weigh slightly less than the mass of a snowflake, might have hit the spacecraft but did not damage it.

“The EPOXI mission spacecraft sailed through Hartley 2’s ice flurries in fine working order and continues to take images as planned of this amazing comet,” said Tim Larson, EPOXI project manager at JPL.

Scientists will need more detailed analysis to determine how long this snow storm has been active, and whether the differences in activity between the middle and ends of the comet are the result of how it formed some 4.5 billion years ago or are because of more recent evolutionary effects.

EPOXI is a combination of the names for the mission’s two components: the Extrasolar Planet Observations and Characterization (EPOCh), and the flyby of comet Hartley 2, called the Deep Impact Extended Investigation (DIXI).

JPL manages the EPOXI mission for the Science Mission Directorate at NASA Headquarters in Washington. The spacecraft was built for NASA by Ball Aerospace & Technologies Corp., in Boulder, Colo.

Advertisements

New Cometary Phenomenon Greets Approaching Spacecraft

Recent observations of comet Hartley 2 have scientists scratching their heads, while they anticipate a flyby of the small, icy world on Nov. 4.

A phenomenon was recorded by imagers aboard NASA’s Deep Impact spacecraft from Sept. 9 to 17 during pre-planned scientific observations of the comet. These observations, when coupled with expected images during the closest encounter with Hartley 2 on Nov. 4, will become the most detailed look yet at a comet’s activity during its pass through the inner-solar system.

NASA's Deep Impact/EPOXI spacecraft flew past Earth on June 27, 2010, to get a boost from Earth’s gravity. It is now on its way to comet Hartley 2, depicted in this artist’s concept, with a planned flyby this fall. Image credit: NASA/JPL-Caltech

“On Earth, cyanide is known as a deadly gas. In space it’s known as one of the most easily observed ingredients that is always present in a comet,” said Mike A’Hearn of the University of Maryland, College Park. A’Hearn is principal of EPOXI, an extended mission that utilizes the already “in flight” Deep Impact spacecraft. “Our observations indicate that cyanide released by the comet increased by a factor of five over an eight-day period in September without any increase in dust emissions,” A’Hearn said. “We have never seen this kind of activity in a comet before, and it could affect the quality of observations made by astronomers on the ground.”

The new phenomenon is very unlike typical cometary outbursts, which have sudden onsets and are usually accompanied by considerable dust. It also seems unrelated to the cyanide jets that are sometimes seen in comets. The EPOXI science team believes that astronomers and interested observers viewing the comet from Earth should be aware of this type of activity when planning observations and interpreting their data.

“If observers monitoring Hartley 2 do not take into account this new phenomenon, they could easily get the wrong picture of how the comet is changing as it approaches and recedes from the sun,” said A’Hearn.

Cyanide is a carbon-based molecule. It is believed that billions of years ago, a bombardment of comets carried cyanide and other building blocks of life to Earth.

The name EPOXI itself is a combination of the names for the two extended mission components: the extrasolar planet observations, called Extrasolar Planet Observations and Characterization (EPOCh), and the flyby of comet Hartley 2, called the Deep Impact Extended Investigation (DIXI). The spacecraft will continue to be referred to as “Deep Impact.”

NASA’s Jet Propulsion Laboratory, Pasadena, Calif., manages the EPOXI mission for NASA’s Science Mission Directorate, Washington. The University of Maryland, College Park, is home to the mission’s principal investigator, Michael A’Hearn. Drake Deming of NASA’s Goddard Space Flight Center, Greenbelt, Md., is the science lead for the mission’s extrasolar planet observations. The spacecraft was built for NASA by Ball Aerospace & Technologies Corp., Boulder, Colo.

The Comet Cometh: Hartley 2 Visible in Night Sky

Backyard stargazers with a telescope or binoculars and a clear night’s sky can now inspect the comet that in a little over two weeks will become only the fifth in history to be imaged close up. Comet Hartley 2 will come within 17.7 million kilometers (11 million miles) of Earth this Wed., Oct. 20 at noon PDT (3 p.m. EDT). NASA’s EPOXI mission will come within 700 kilometers (435 miles) of Hartley 2 on Nov. 4.

This image of comet Hartley 2 was captured by amateur astronomer Byron Bergert on Oct. 4 in Gainesville, Florida using a 106 mm Takahashi astrograph. Image credit: Byron Bergert

“On October 20, the comet will be the closest it has ever been since it was discovered in 1986 by Australian astronomer Malcolm Hartley,” said Don Yeomans, head of NASA’s Near-Earth Object Office at the Jet Propulsion Laboratory in Pasadena, Calif. and a member of the EPOXI science team. “It’s unusual for a comet to approach this close. It is nice of Mother Nature to give us a preview before we see Hartley 2 in all its cometary glory with some great close-up images less than two weeks later.”

Comet Hartley 2, also known as 103P/Hartley 2, is a relatively small, but very active periodic comet that orbits the sun once every 6.5 years. From dark, pristine skies in the Northern Hemisphere, the comet should be visible with binoculars as a fuzzy object in the constellation Auriga, passing south of the bright star Capella. Viewing of Hartley 2 from high ambient light locations including urban areas may be more difficult.

In the early morning hours of Oct. 20, the optimal dark sky window for mid-latitude northern observers is under two hours in length. This dark interval will occur between the time when the nearly-full moon sets at about 4:50 a.m. (local time) and when the morning twilight begins at about 6:35 a.m.

By October 22, the comet will have passed through the constellation Auriga. It will continue its journey across the night sky in the direction of the constellation Gemini.

EPOXI is an extended mission that utilizes the already “in-flight” Deep Impact spacecraft to explore distinct celestial targets of opportunity. The name EPOXI itself is a combination of the names for the two extended mission components: the extrasolar planet observations, called Extrasolar Planet Observations and Characterization (EPOCh), and the flyby of comet Hartley 2, called the Deep Impact Extended Investigation (DIXI). The spacecraft will continue to be referred to as “Deep Impact.”

JPL manages the EPOXI mission for NASA’s Science Mission Directorate, Washington. The University of Maryland, College Park, is home to the mission’s principal investigator, Michael A’Hearn. Drake Deming of NASA’s Goddard Space Flight Center, Greenbelt, Md., is the science lead for the mission’s extrasolar planet observations. The spacecraft was built for NASA by Ball Aerospace & Technologies Corp., Boulder, Colo.

%d bloggers like this: