NASA's 3-D Study of Comets Reveals Chemical Factory at Work

This rotating 3-D map shows how HNC molecules (made of hydrogen, carbon and nitrogen) are released from the nucleus of comet Lemmon and then spread evenly throughout the atmosphere, or coma. 

Similar maps revealed that HNC and formaldehyde are produced in the coma, rather than the comet's nucleus. 

Image courtesy Brian Kent /NRAO /AUI /NSF.

A NASA-led team of scientists has created detailed 3-D maps of the atmospheres surrounding comets, identifying several gases and mapping their spread at the highest resolution ever achieved.

"We achieved truly first-of-a-kind mapping of important molecules that help us understand the nature of comets," said Martin Cordiner, a researcher working in the Goddard Center for Astrobiology at NASA's Goddard Space Flight Center in Greenbelt, Maryland. Cordiner led the international team of researchers.

Almost unheard of for comet studies, the 3-D perspective provides deeper insight into which materials are shed from the nucleus of the comet and which are produced within the atmosphere, or coma.

This helped the team nail down the sources of two key organic, or carbon-containing, molecules.

The observations were conducted in 2013 on comets Lemmon and ISON using the Atacama Large Millimeter/submillimeter Array (ALMA), a network of high-precision antennas in Chile. These comets are the first to be studied with ALMA.

The ALMA observations combine a high-resolution 2-D image of a comet's gases with a detailed spectrum at each point.

From these spectra, researchers can identify the molecules present at every point and determine their velocities (speed plus direction) along the line-of-sight; this information provides the third dimension - the depth of the coma.

"So, not only does ALMA let us identify individual molecular species in the coma, it also gives us the ability to map their locations with great sensitivity," said Anthony Remijan, a scientist with the National Radio Astronomy Observatory, one of the organizations that operates ALMA, and a co-author of the study.

The researchers reported results for three molecular species, focusing primarily on two whose sources have been difficult to discern (except in comet Halley).

The 3-D maps indicated whether each molecule was flowing outward evenly in all directions or coming off in jets or in clumps.

In each comet, the team found that two species - formaldehyde and HNC (made of one hydrogen, one nitrogen and one carbon) - were produced in the coma.

For formaldehyde, this confirmed what researchers already suspected, but the new maps contained enough detail to resolve clumps of the material moving into different regions of the coma day-by-day and even hour-by-hour.

For HNC, the maps settled a long-standing question about the material's source. Initially, HNC was thought to be pristine interstellar material coming from the nucleus of a comet, whereas later work suggested other possible sources.

The new study provided the first proof that HNC is produced during the breakdown of large molecules or organic dust in the coma.

"Understanding organic dust is important, because such materials are more resistant to destruction during atmospheric entry, and some could have been delivered intact to early Earth, thereby fueling the emergence of life," said Michael Mumma, Director of the Goddard Center for Astrobiology, and a co-author on the study.

"These observations open a new window on this poorly known component of cometary organics."

Comet ISON drawn in by Sun's gravity and burns up - Video

The comet has most likely disintegrated under the high heat and gravitational stress of the Sun on Nov. 28, 2013. 

It is not visible in Solar Dynamics Observatory (SDO) footage and NASA scientists confirmed that they do not see it. 

 Credit: NASA / SDO / SOHO

NASA STEREO: Watching Comet ISON - Video

This movie from NASA's STEREO spacecraft's Heliospheric Imager shows Comet ISON, Mercury, Comet Encke andEarth over a five-day period from Nov. 20 to Nov. 25, 2013. 

The sun sits to the right of the field of view of this camera. 

Credit: NASA/STEREO

Comet ISON Dances near the Sun

In this photo provided by NASA, a contrast-enhanced image produced from the Hubble images of comet ISON taken April 23, 2013 reveals the subtle structure in the inner coma of the comet. 

In this computer-processed view, the Hubble image has been divided by a computer model coma that decreases in brightness proportionally to the distance from the nucleus, as expected for a comet that is producing dust uniformly over its surface. 

ISON's coma shows enhanced dust particle release on the sunward-facing side of the comet's nucleus, the small, solid body at the core of the comet. 

This information is invaluable for determining the comet's shape, evolution, and spin of the solid nucleus. (AP Photo/NASA)

Comet ISON is teasing the solar system as it dances with the sun and it's giving astronomers mixed signals.

Will it meet a fiery death—or survive—when it whips around the sun on Thursday?

The icy comet will be only about 1 million miles ( 1.6 million kilometers) away from the sun's super-hot surface during its close encounter on US Thanksgiving day.

On Monday, it looked like it was about to die even before it got there. On Tuesday, it appeared healthy again.

"We have never seen a comet like this," Naval Research Laboratory astrophysicist Karl Battams said during a NASA news conference Tuesday. "It has been behaving strangely."

Because it is so close to the sun, ISON will likely not be visible from Earth on Thursday—except via a fleet of NASA telescopes and spacecraft aimed at the comet as it gets closest to the sun at 1:37 p.m. EST( (1837 GMT), he said and it will be a few hours before scientists know whether the comet survives.

But even if the comet dies, Johns Hopkins University scientist Carey Lisse said there's a good chance that people on Earth will get an interesting cosmic show.

The comet's remnants could paint the sky with a wide swath of green in the Northern Hemisphere.

Comet ISON Now Visible to Naked Eye After Outburst - Video

The much-anticipated Comet ISON is now visible to the naked eye according to reports from many observers.

Comet ISON — the potential "comet of the century" — has suddenly brightened in an outburst of activity with just two weeks to go before it grazes the surface of the sun.

In recent months, Comet ISON has repeatedly befuddled forecasters trying to anticipate just how bright it will ultimately become. But earlier this week, the comet's brightening trend again seemed to sputtering and stalling, but more recent observations suggest a sudden and radical upsurge in brightness.

NASA's Spitzer observes gas emission from comet ISON

These images from NASA's Spitzer Space Telescope of C/2012 S1 (Comet ISON) were taken on June 13, when ISON was 310 million miles (about 500 million kilometers) from the sun.

Credit: NASA/JPL-Caltech/JHUAPL/UCF

Astronomers using NASA's Spitzer Space Telescope have observed what most likely are strong carbon dioxide emissions from Comet ISON ahead of its anticipated pass through the inner solar system later this year.

Spitzer's Infrared Array Camera

Images captured June 13 with Spitzer's Infrared Array Camera indicate carbon dioxide is slowly and steadily "fizzing" away from the so-called "soda-pop comet," along with dust, in a tail about 186,400 miles (300,000 kilometers) long.

"We estimate ISON is emitting about 2.2 million pounds (1 million kilograms) of what is most likely carbon dioxide gas and about 120 million pounds (54.4 million kilograms) of dust every day," said Carey Lisse, leader of NASA's Comet ISON Observation Campaign and a senior research scientist at the Johns Hopkins University Applied Physics Laboratory in Laurel, Md.

"Previous observations made by NASA's Hubble Space Telescope and the Swift Gamma-Ray Burst Mission and Deep Impact spacecraft gave us only upper limits for any gas emission from ISON.

Carey Lisse

Thanks to Spitzer, we now know for sure the comet's distant activity has been powered by gas."

Comet ISON was about 312 million miles (502 million kilometers) from the sun, 3.35 times farther than Earth, when the observations were made.

"These fabulous observations of ISON are unique and set the stage for more observations and discoveries to follow as part of a comprehensive NASA campaign to observe the comet," said James L. Green, NASA's director of planetary science in Washington. "ISON is very exciting.

We believe that data collected from this comet can help explain how and when the solar system first formed."

Comet ISON (officially known as C/2012 S1) is less than 3 miles (4.8 kilometers) in diameter, about the size of a small mountain, and weighs between 7 billion and 7 trillion pounds (3.2 billion and 3.2 trillion kilograms).

Because the comet is still very far away, its true size and density have not been determined accurately.

Like all comets, ISON is a dirty snowball made up of dust and frozen gases such as water, ammonia, methane and carbon dioxide. These are some of the fundamental building blocks, which scientists believe led to the formation of the planets 4.5 billion years ago.

Comet ISON is believed to be inbound on its first passage from the distant Oort Cloud, a roughly spherical collection of comets and comet-like structures that exists in a space between one-tenth light-year and 1 light-year from the sun. The comet will pass within 724,000 miles (1.16 million kilometers) of the sun on Nov. 28.

It is warming up gradually as it gets closer to the sun. In the process, different gases are heating up to the point of evaporation, revealing themselves to instruments in space and on the ground. Carbon dioxide is thought to be the gas that powers emission for most comets between the orbits of Saturn and the asteroids.

The comet was discovered Sept. 21, roughly between Jupiter and Saturn, by Vitali Nevski and Artyom Novichonok at the International Scientific Optical Network (ISON) near Kislovodsk, Russia.

This counts as an early detection of a comet, and the strong carbon dioxide emissions may have made the detection possible.

"This observation gives us a good picture of part of the composition of ISON, and, by extension, of the proto-planetary disk from which the planets were formed," said Lisse.

"Much of the carbon in the comet appears to be locked up in carbon dioxide ice. We will know even more in late July and August, when the comet begins to warm up near the water-ice line outside of the orbit of Mars, and we can detect the most abundant frozen gas, which is water, as it boils away from the comet."

NASA Deep Impact Probe Snaps Photos of Comet ISON

The comet that may put on a spectacular light show during a November date with the Sun, was observed by the Deep Impact mission. The spacecraft has also had close fly-bys of comet's Tempel 1 and Hartley 2 and scientific observations of Garradd.

CREDIT: NASA/JPL-Caltech/UMD (Tony Farnham)

A NASA spacecraft has captured its first photos of comet ISON, an icy wanderer that some scientists say could dazzle as a "comet of the century" when it swings through the inner solar system later this year.

The photos were taken by NASA's Deep Impact probe and reveal comet ISON as a bright, dusty ball moving against a star-filled background. The spacecraft snapped the pictures on Jan. 17 and Jan. 18 from a distance of about 493 million miles (793 million kilometers).

Comet ISON has been the focus of much anticipation among scientists and stargazers because of its potential to put on a spectacular display in late November, when it makes its closest approach to the sun.

Some forecasts predict the comet could shine brighter than the full moon. As of mid-January, the comet's tail was more than 40,000 miles (64,400 km).

Some projections state that comet ISON, which is officially designated comet C/20012 S1 (ISON), could shine extremely bright in the nighttime sky, possibly even rivaling the full moon.

Whether the comet will meet expectations or fizzle out remains to be seen, but it has already become a target for NASA and amateur astronomers.

"This is the fourth comet on which we have performed science observations and the farthest point from Earth from which we've tried to transmit data on a comet," Deep Impact project manager Tim Larson, of the agency's Jet Propulsion Laboratory in Pasadena, Calif., said in a statement Tuesday (Feb. 5) "The distance limits our bandwidth, so it's a little like communicating through a modem after being used to DSL. But we're going to coordinate our science collection and playback so we maximize our return on this potentially spectacular comet."