Comet Elenin Is Fading; Doodlebugs On Mars?

Pictures taken on Aug. 19 and 23 with the same equipment and exposure show how much the comet has faded in recent days. The photos were made with a standard camera lens and don't show the tail like 'deeper' images taken through a telescope. Credit: Rob Kaufman

The other day I wrote how unpredictable comets can be, one of the main reasons they’re so fun to follow by eye and telescope. After a nice show of steady brightening in the last few weeks, at least two dedicated comet observers – Michael Mattiazzo and Rob Kaufman in Australia – observed that C/2010 X1 Elenin has faded by about a full magnitude (a factor of 2 1/2) over the past several nights. Not good news, but not the end of the world either. Comets brighten and fade as “jets” of vaporizing ice entrained with dust turn on and off on its surface.

Animation of Comet Elenin from four pictures taken on Aug. 23 through an 11-inch telescope. Credit: Michael Mattiazzo

I’d rather it would continue to brighten toward a naked eye display this October when the comet’s closest to Earth. It still might, but it’s also possible that Elenin may fizzle out, especially if the fragile comet nucleus were to break into pieces.

Michael’s animation shows a slight elongation of the larger, bright nuclear region, the fuzzy, dusty area that hides the comet itself. Could it be an indication of a break up? We can’t be sure, but time will tell.  For all we know, Comet Elenin will return to its previous brightness expectations next week. For more photos and animations, I encourage you to visit Michael Mattiazzo’s Southern Comets Homepage.

As a kid, I remember discovering a doodlebug or antlion in the dirt along the side of a friend’s house. I watched as this insect larva with giant claw-like jaws waited at the bottom of its little sand trap for hapless ants to tumble down the steep sides literally into the jaws of death.  Tough world, but you gotta make a living.

An antlion sand trap. The insect waits beneath the hole with only its jaws sticking out. Credit: Wiki

This particular method of catching your food struck me as positively ingenious. Naturally we wanted to help out the antlion as well as watch the gruesome act of eating, so we looked around for random ants and dropped them along the “crater” rim, then pulled up close to wait for the inevitable. Anticipation can be a delicious emotion. Nature is always fascinating but especially through a child’s eyes. Children have an instinctive understanding of one nature’s universal principles: Eat or get eaten.

A skylight opening to an underground cavern in a small crater on Mars. Based on the shadow cast on the pit floor, the cave is about 65 feet deep. You can see how material has slid down the walls into the hole. Click to enlarge. Credit: NASA/JPL/University of Arizona

That’s why this recently released photo taken by the Mars Reconnaissance Orbiter of a crater with a hole in its center immediately brought to mind the antlion. I don’t mean to imply a real connection of course, but if you’re looking for a perfect setting for a science fiction story of alien antlions vs. humanity, this might be it.

The crater lies atop the slopes of the extinct Martian volcano Pavonis Mons, and the opening, which measures 115 feet across, is a skylight or entry to an underground cavern.

“Caves often form in volcanic regions like this when lava flows solidify on top, but keep flowing underneath their solid crust. These, now underground, rivers of lava can then drain away leaving the tube they flowed,” according to NASA writer Shane Byrne.

Later this year, the spacecraft will take another image of the cave from a slightly different angle to create a stereo pair that scientists hope will help them determine just how the hole formed. To see more photos of caves on Mars, click HERE.

6 Responses

  1. jessie leigh

    So bob another question! : )

    So if Elenin is fading is that a bad thing? or a good thing?

    if bad then why is it bad?

    1. astrobob

      Jessie — Fading is neither good nor bad, it’s just a comet being a comet. However, from an observer’s perspective, I’d rather it would become brighter and more spectacular to see. There’s still plenty of time for that to happen … I hope!

  2. I saw a light fall from the sky around 10pm in Southwestern Minnesota last night. The bottom of the light the closer it got to earth was greenish. It didn’t act like a falling star.

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