A comet tale plus an asteroid pummeling

Posted Jan. 4, 2013

Last night I attached my camera to a battery-operated mount designed to track the stars. What a comedy. Polar alignment kept slipping, the camera-lens weight was too much for the mount and focusing the telephoto lens proved tedious. All I wanted was a single picture of comet C/2012 K5. In the end, I got a lot of exercise hopping back and forth making adjustments … and a somewhat serviceable image.

The comet had faded a bit but was still a fuzzy blotch in binoculars and showed an obvious northeastward-pointing tail at low magnification through the telescope. Although the tail color was too subtle to be seen with the eye, a time exposure reveals the yellow tint caused by sunlight reflecting off dust particles. Heat from the sun vaporizes comet ice, releasing embedded rocks and dust into the tail behind the comet’s head.

Not much news has been reported from the Curiosity rover of late. NASA mission specialists are probably happy they can work in peace out of the media spotlight. Pictures keep pouring in just the same. You can view the most recent set of raw images here: http://1.usa.gov/13gF08T.

The rover’s been exploring a shallow basin called Yellowknife Bay. It’s one bleak-looking landscape that begs for the introduction of a few saguaro cacti. After finishing up exploration of the bay, scientists plan to spend most of 2013 piloting the rover toward the mission’s primary science destination — the 3-mile-high layered mound at center of Gale Crater center named Mt. Sharp. There the robot will study and sample water-rich clays deposited long ago when Mars was a wetter world.

A recent paper published in the November-December issue of the journal Icarus describes the dark splotches of carbon-containing materials exposed along the rims of small craters as well as along the edges of the huge impact craters Rheasilvia and Venenaeia on the asteroid Vesta.

NASA’s Dawn mission to Vesta last year took thousands of photos, some of which show dark patches of carbonaceous (car-bon-NAY-shuss) material that matches the dark, carbon-rich mineral fragments found in Vesta meteorites here on Earth.

“The dark material was most probably delivered during the formation of the older Veneneia basin (large impact crater in Vesta’s southern hemisphere) when a slow impacting asteroid collided with Vesta. Dark material from this two to three billion year old basin was covered up by the impact that Dark material from this two to three billion year old basin was covered up by the impact that subsequently created the Rheasilvia basin,” according to Lucille Le Corre and Vishnu Reddy, lead authors of the study.

The scientists measured the light from the dark patches on Vesta and discovered they were made of the same material as the dark carbon-rich fragments inside a group of fallen space rocks called eucrites and Howardites.

Asteroids, many of which orbit in the main belt between Mars and Jupiter, come in all flavors. Some are made of bone-dry, rocky materials, others contain clays and water and still others are nearly pure metal. Bashing and smashing into one another they left their marks not only on each other but in the pieces that came (and still come) to Earth.

Read more about the new study here: http://bit.ly/VD6IIr.

King, photo editor at the

Duluth News Tribune and

amateur astronomer, blogs at astrobob.areavoices.com

Tags: life, science