Rosetta Finds Its Stone

A  view of Comet 67P/Churyumov-Gerasimenko taken by Rosetta’s OSIRIS narrow-angle camera on Aug. 3 from a distance of 177 miles. (European Space Agency image.)

A view of Comet 67P/Churyumov-Gerasimenko taken by Rosetta’s OSIRIS narrow-angle camera on Aug. 3 from a distance of 177 miles. (European Space Agency image.)

The European Space Agency’s Rosetta spacecraft achieved orbit around Comet 67P/Churyumov-Gerasimenko on August 6. Ten years on the way, traveling four billion miles and aided by four gravity assists (three from Earth and one from Mars), Rosetta will escort the comet as it swings around the Sun and heads back toward Jupiter.

The Alice ultraviolet imaging spectrometer.

The Alice ultraviolet imaging spectrometer.

Rosetta will study the comet an OSIRIS camera, a MIRO miniature radio telescope, an Alice ultraviolet (UV) spectrograph, an Ion and Electron Sensor (IES) and other instruments.

Rosetta also carries a lander, Philae, that will be dropped on the comet’s surface in November 2014, where it will drill, extract and analyze samples, and send pictures back to Earth.

Based on temperature readings made by Rosetta’s instruments, scientists already have surmised that the comet has a porous, dusty crust with ice beneath. The surface is strewn with boulders the size of houses, and Churyumenko-Gerasimov’s icy cliffs rise as high as 500 feet (150 meters).

Rosetta initially will orbit about 60 miles from the comet, but eventually will move in closer, about 12 to 20 miles away.

Update 08/07/2014: Corrected misspelling of “ultraviolent” spectrograph.

Comet Ready For Its Close-Up

Photographers in the Southern Hamisphere have been snapping beautiful pictures of Comet Panstarrs – see examples at Earthsky.org. In a few days it’ll be our turn. If we’re lucky it might be visible to the unaided eye.

As seen from mid-northern latitudes, Comet Panstarrs might become visible with an optical aid around March 7 or 8. However, the comet will sit in the glow of dusk and will set around 40 to 45 minutes after sunset. By March 12, the comet will be considerably higher in the sky and will set around 75 minutes after sun. What’s more, the comet will be next to the waxing crescent moon on the North American evening of March 12.

The comet will pass closest to the sun on March 10, when it’s expected to be at its brightest.

[Thanks to John King Tarpinian for the story.]

NASA’s Cometary Enterprise

Hartley 2

Once upon a time a spacecraft really did have a five-year mission.

It is NASA’s EPOXI spacecraft, which paid its second visit to a comet since 2005 when it flew past and photographed the Hartley 2 comet on November 4.

The EPOXI mission is recycling the Deep Impact spacecraft, whose probe intentionally collided with comet Tempel 1 on July 4, 2005, revealing, for the first time, the inner material of a comet. In fact, I have been able to find a whole riff I did about comets, with a preview of Deep Impact’s first mission for the late, lamented Trufen.net (scroll down).

CNN’s coverage of today mission used the word “survived” in its lead, dramatically implying the spacecraft had gone in harm’s way:

A spacecraft survived the closest encounter ever with a comet on Thursday, tracking it just 435 miles (700 kilometers) from the comet’s nucleus.

Since 435 miles is farther than Los Angeles is from San Francisco my initial reaction wasn’t to gasp in amazement. Yet people in San Francisco give the impression they’d like to be even farther away, so who can say? NASA also says comet Hartley 2 is “much more active” than Tempel 1, the previous comet visited by Deep Impact, despite being smaller. Smaller and much more active – there’s San Francisco all over again.

Amateur skywatchers may be able to see Hartley 2 in a dark sky with binoculars or a small telescope.

Omnivores Not to Blame
for Mammoth Extinction?

mammoth hunters

Blame a swarm of comets striking North America 12,900 years ago for the environmental disaster that caused the extinction of mammoths and many other species, say scientists quoted in a CNN report.

“The nanodiamonds that we found at all six locations exist only in sediments associated with the Younger Dryas Boundary layers, not above it or below it,” said University of Oregon archaeologist Douglas Kennett. “These discoveries provide strong evidence for a cosmic impact event at approximately 12,900 years ago that would have had enormous environmental consequences for plants, animals and humans across North America.”

An earlier theory advanced to explain the mass extinction in North America of half of the animal species weighing more than 100 pounds is that when Man migrated over the Bering land bridge, he ate all of them. Not on the very first day, of course.

I don’t know if I’m ready to abandon that theory, either. I find it incredibly easy to believe after a nonstop week of Christmas-to-New-Year’s feasting.