Tag: comets

A History of Comet Collisions Inscribed in Saturn & Jupiter's Rings

By Patrick Morgan | April 3, 2011 9:39 am

What’s the News: Looking at images of odd undulations in the rings of Saturn and Jupiter, astronomers have discovered that comets are to blame. The finding means that a planet’s rings act as a historical record of passing comets, possibly leading to a better understanding of comet populations. “We now know that collisions into the rings are very common—a few times per decade for Jupiter and a few times per century for Saturn,” Mark Showalter, from the SETI Institute in Mountain View, California, told the Daily Mail. “Now scientists know that the rings record these impacts like grooves in a vinyl record, and we can play back their history later.”

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NASA's Stardust Prepares a Valentine's Day Pass of Comet Tempel 1

By Andrew Moseman | February 14, 2011 10:01 am

Six years ago, NASA visited the comet Tempel 1 with a fury: Its Deep Impact mission launched a projectile into the comet that kicked up dust and ice for the spacecraft to capture as a sample. Tonight, NASA is taking another pass by the comet—but a little more gently this time.

The hardy Stardust explorer, which has passed by other comets and brought samples back to Earth, will pass by Tempel 1 tonight to try to get a good look at what NASA’s blast did to the comet. Last time around, Deep Impact’s projectile was actually too effective. It blasted so much debris off the comet that it blinded itself.

Now, Stardust will be able to obtain images of that crater up close for the first time. Moreover, in the nearly six years since that initial encounter, the comet has completed an orbit around the solar system, passing close to the sun. “For the first time, we’ll go back to see what happens to a comet” after it passes close to the sun, said Pete Schultz of Brown University, a scientist for the new mission, which has been dubbed Stardust-NExT. [Los Angeles Times]

Stardust’s pass presents an opportunity not just to see what’s changed in the last five to six years of the comet’s life, but also to peel back more of Tempel 1‘s ancient history.

“Here’s a chance where we can see what has changed, how much has changed,” said Joseph Veverka, a professor of astronomy at Cornell and the mission’s principal investigator, “so we’ll start unraveling the history of a comet’s surface.” For example, photographs taken by Deep Impact in 2005 showed areas that looked old and others that seemed much younger. But the snapshots did not tell the ages of any of them. “We have no idea whether we’re talking about things that have been there for a hundred years, a thousand years, a million years,” Dr. Veverka said. [The New York Times]

The flyby is scheduled to begin at about 11:30 p.m. Eastern tonight (Monday). Stardust should pass within about 125 miles of the comet, taking snapshots of the cosmic traveler and also catching some of the particles flying off it. The approach will mark the first time two spacecraft have studied the same comet up close, and probably mark the last hurrah for Stardust: After returning with samples from the comet Wild 2 in 2004, the craft was still running fine and got the OK from NASA to go on this second comet chase. But after a dozen years in space logging billions of millions, Stardust will soon be, simply, out of fuel.

Related Content:
80beats: Photo: Comet Hartley 2 Travels With a Posse of Snowballs
80beats: NASA Probe Has a Valentine’s Day Date With a Comet
Bad Astronomy: Amazing Close-Ups of Comet Hartley 2!
Bad Astronomy: Ten Things You Don’t Know About Comets
DISCOVER: 11 Space Missions That Will Make Headlines in 2011 (photo gallery)

Image: NASA


NASA Probe Has a Valentine's Day Date With a Comet

By Eliza Strickland | January 19, 2011 5:06 pm

This NASA probe had its Valentine’s Day plans set well in advance. On February 14 at 11:37 p.m. eastern time, the Stardust-NExT spacecraft will swoop past the comet Tempel 1 to snap photos and collect data about this solar system wanderer. The probe will pass just 124 miles from Tempel 1.

Tempel 1 is of particular interest because another probe has dallied with it in the past: In 2005, NASA’s Deep Impact probe approached and fired an 800-pound impactor at the comet’s surface to study its composition. While that mission was a success, the dust kicked up from the crash prevented the Deep Impact probe from getting a good look at the crater created. By sending Stardust-NExT along now, researchers can finally get a good look at the crater.

And that’s not all they’ll be looking at.

Since the 2005 impact, the comet has passed closer to the sun and then headed out to the orbit of Jupiter, before heading back for another visit to the inner solar system. The team hopes to see not only the size of the crater plowed by the 2005 impact, but also to see how a close pass by the sun resurfaces a comet. “We’re going to find out a lot about how comets evolve,” says Stardust-NExT co-investigator Steve Chesley. [USA Today]

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Photo: Comet Hartley 2 Travels With a Posse of Snowballs

By Eliza Strickland | November 19, 2010 3:28 pm

Phil Plait has the report on NASA’s latest pictures from the flyby of Hartley 2, which reveal that the comet is surrounded by a blizzard of snow and ice:

Wow! Most of those dots are not stars: they are actual snowballs, frozen matter that has been ejected by the comet itself! They range in size from a few centimeters to a few dozen across, so they really are about the size of snowballs you’d use in a snowball fight… or to make a snowman. But I wouldn’t recommend it: a lot of that material is not frozen water, it’s actually frozen carbon dioxide, or dry ice.

Find out what else we’ve learned about Hartley 2 and see more photos at Bad Astronomy.

Related Content:
Bad Astronomy: Amazing Close-Ups of Comet Hartley 2!
80beats: Holy Hartley 2! What to Know About NASA’s Comet Flyby
80beats: Video: Comet Caught Crashing into the Sun
80beats: Spacecraft-Collected Comet Dust Reveals Surprises From the Solar System’s Boondocks
Bad Astronomy: Ten Things You Don’t Know About Comets

Image: NASA / JPL-Caltech / UMD


Comet Flyby Yields Close-ups of the Lumpy, Icy Hartley 2

By Eliza Strickland | November 4, 2010 12:31 pm

Hartley2This morning, NASA’s EPOXI mission whizzed by the comet Hartley 2, coming as near as 450 miles to the comet at 8 a.m. and snapping pictures all the while. The icy comet is less than a mile in diameter and has an irregular shape that one NASA researcher recently described as “a cross between a bowling pin and a pickle.”

The images are already streaming in: Head to Bad Astronomy for more pictures and a discussion of what these snapshots tell us about Hartley 2.

This is the second cometary encounter for this spacecraft–under a previous mission called Deep Impact the spacecraft sent an impactor hurtling into the comet Tempel 1, allowing the craft to photograph the excavated debris and the impact crater.

Related Content:
80beats: Holy Hartley 2! What to Know About NASA’s Comet Flyby
80beats: Video: Comet Caught Crashing into the Sun
80beats: Spacecraft-Collected Comet Dust Reveals Surprises From the Solar System’s Boondocks
Bad Astronomy: Ten Things You Don’t Know About Comets
DISCOVER: NASA Takes a Wild Comet Ride



Holy Hartley 2! What to Know About NASA's Comet Flyby

By Andrew Moseman | October 26, 2010 4:59 pm

hartley2On November 4, NASA’s mission EPOXI will make a flyby less than 450 miles from the comet Hartley 2. Here’s what to know about this dirty snowball.

1. It’s a frequent visitor.

Malcolm Hartley discovered this namesake comet 24 years ago, and it’s returned to swing around the sun a few times since.

Like the famous Halley’s Comet, Comet Hartley 2 is a periodic comet that follows a years-long loop around the sun. It takes 6.46 years to complete one circuit, compared with Halley’s 75.3 years. [Christian Science Monitor]

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Scientist Smackdown: No Proof That a Comet Killed the Mammoths?

By Andrew Moseman | August 31, 2010 4:02 pm

MammothWhen it comes to explaining why the woolly mammoths died out, “death from above” could be down for the count.

Nearly 13,000 years ago, North American megafauna like the mammoths and giant sloths—and even human groups like the people of the Clovis culture—disappeared as the climate entered a cold snap. As DISCOVER has noted before, there’s been a controversial hypothesis bubbling up saying that a comet impact caused it all, but other scientists have been shooting holes in that idea of the last couple years. In a study in this week’s Proceedings of the National Academy of Sciences, a team led by Tyrone Daulton pooh-poohs what may be the last major evidence that supports the impact idea.

That evidence takes the shape of nano-diamonds in ancient sediment layers, a material said to form during impacts only.

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CATEGORIZED UNDER: Human Origins, Living World

Perseid Meteor Shower: Where & When to Catch the Sky Show

By Andrew Moseman | August 11, 2010 10:25 am

PerseidsThis week brings the annual return of the Perseids, one of the most stunning meteor showers of the year, visible from just about anywhere.

WHAT: The height of the Perseid shower comes every August, because that’s the time our planet passes through a certain debris path.

The Perseids are created by the tiny remnants left behind by comet Swift-Tuttle. The Earth passes through this material once a year, creating a spectacular show as the cometary particles burn up in the atmosphere [Discovery News].

WHERE: Like the Orionid meteors, which come around in October, the Perseids are so named because of the constellation from which they appear to originate.

If you trace the Perseid meteor trails backward, they meet within the constellation Perseus the Hero; this is how the shower got its name [Astronomy].

WHEN: Tonight (Wednesday) through Friday night we’ll see the height of Perseid visibility once the sky reaches full darkness, from 11 p.m. to midnight wherever you might be until the first light of dawn. On Friday night the crescent moon will set before twilight ends, giving stargazers a dark sky to gaze at.

Swift-Tuttle’s debris zone is so wide, Earth spends weeks inside it. Indeed, we are in the outskirts now, and sky watchers are already reporting a trickle of late-night Perseids. The trickle could turn into a torrent between August 11th and 13th when Earth passes through the heart of the debris trail [NASA Science News].

Indeed, the opening shot of the Perseids appeared as a bright fireball over Alabama on August 3.

WHAT YOU NEED: Your two eyes, and a place away from the city lights. For more cool Perseid details, check out Astronomy’s coverage.

Follow DISCOVER on Twitter

Related Content:
80beats: Found on a Martian Field: A Whomping Big Meteorite
80beats: Study: 20-Million-Year Meteorite Shower Turned Earth Warm & Wet
80beats: Scientists Pick Up the Pieces (Literally) of an Asteroid Spotted Last October
80beats: Perseid Meteor Shower Should Dazzle Despite a Bright Moon (2009 edition)

Image: flickr / aresauburn


Study: A Death Star Named Nemesis Isn’t to Blame for Mass Extinctions

By Joseph Calamia | July 13, 2010 1:52 pm

earthcollideIn the 1980s, fossil record research showed a curious cycle: Every 27 million years, Earth hosted a mass extinction. Some scientists suggested that a dim star dubbed Nemesis was in a deadly dance with our sun, periodically kicking comets out of the distant Oort Cloud to shower our planet with destruction. Morbidly fascinating as it may be, the authors of a new study argue that this “death star” theory doesn’t hold up.

The cyclical extinctions do make a solid pattern, say Adrian Melott of the University of Kansas and Richard Bambach of Smithsonian Institution Museum of Natural History, whose paper is available through arXiv.org. The two have gone back in the record to 500 million years ago, further than any other researchers, and have confirmed the 27 million year cycle at a 99 percent confidence.

According to Bambach, there’s no doubt at all that every 27 million years-odd, huge numbers of species suddenly become extinct. He says this is confirmed by “two modern, greatly improved paleontological datasets of fossil biodiversity” and that “an excess of extinction events are associated with this periodicity at 99% confidence”. This regular mass slaughter has apparently taken place around 18 times, back into the remote past of half a billion years ago. [The Register]

The problem, Nemesis fans, is that the cycle is too precise, the researchers say. If these extinctions result from a dance between our sun and Nemesis, the researchers note, the period of these mass extinctions would change as other stars buffeted the pair and changed the courses of Nemesis’s orbit around the sun.

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CATEGORIZED UNDER: Living World, Space

Asteroid Photo Session: Rosetta Spacecraft Snaps Pics of Battered Lutetia

By Joseph Calamia | July 12, 2010 10:11 am

LutetiaOn Saturday, the European Space Agency’s Rosetta probe took the world’s closest pictures of the 80- by 50-mile-wide asteroid known as 21 Lutetia. Though the Lutetia visit is just a stop on the way to Rosetta’s real destination–a 2014 visit to the comet 67P/Churyumov-Gerasimenko–Saturday’s pictures document the closest visit to this big asteroid, the largest we’ve ever visited with a spacecraft.

We’ve known about Lutetia for quite a while: since 1852, according to Sky and Telescope. In November of that year, Hermann Goldschmidt spotted the space rock from his Paris balcony. The asteroid is now around 280 million miles from the Sun. From only 2,000 miles away, Rosetta got a much closer look at Lutetia, whipping around it at about 10 miles per second (30,000 miles per hour) as its OSIRIS camera snapped pictures recording details down to a few dozen meters.

“The fly-by has been a spectacular success with Rosetta performing fautlessly,” ESA said in a statement. “Just 24 hours ago, Lutetia was a distant stranger. Now, thanks to Rosetta, it has become a close friend.” [AFP]

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