8 July 2009

Noctilucent Clouds, The Shuttle, Siberia and Myth Busters

Posted by Dan Satterfield

Yes they all have something in common.

One of the negatives of working as a Meteorologist in TV, is that you are usually the only one on duty who has a background, and avid interest in science. The rest are (and I love them) News Weasels! ( I actually work with a bunch of supremely talented people, who save me from my grammar frequently)

Image from 1908 Tunguska Blast in Siberia

Image from 1908 Tunguska Blast in Siberia

One of our directors is the son of two scientists, His Mother is a Chemist and his late Father had a PhD in Physics and was an expert in materials. We talk daily about science topics, and I really feel he should go into science, he has an incredibly inquisitive mind, and loves a mystery (Kids never seem to follow their parents careers- do they?).

Daniel is moving to Orlando soon and I will miss our conversations greatly. When I found out the Universe could expand faster than c, he was the only one at work who really appreciated the glory of the idea!

He told me today of Michael Kelley, an Atmospheric Scientist at Cornell, who noticed something weird. Often, three days after a shuttle launch, a display of Noctilucent clouds shows up in Alaska! Sure enough Kelley has a paper in press about this in Geophysical Research Letters.

Noctilucent Clouds credit NASA/Veres Viktor

Noctilucent Clouds credit NASA/Veres Viktor

Noctilucent clouds are very rare clouds that form about 50 miles high at the edge of the Thermosphere and Mesosphere. They are called night shining clouds, because at that altitude they can be lit by the sun when it is totally night below (No I have never seen them, but I carry extra underwear just in case).

He apparently discovered this from research into these clouds, and he also discovered a brilliant display in England in 1908. Right after the famous Tunguska blast in Siberia. It’s long been thought this blast, which leveled trees for hundreds of miles, and produced the energy of 200 atom bombs, was a meteoroid hitting Earth’s atmosphere. This may very well confirm that it was a comet that did it! The Tunguska meteorite blew up before hitting the ground, and this leads us to the TV show Mythbusters.

In a recent episode, they guys were amazed that if you put thermite in a can on top of a block of ice, the ice would explode! (see the video boys and girls!)

Daniel and I watched the video and discussed the Physics of it. We were uncertain. Daniel thought to call his Mom, who NASA trusts for chemistry knowledge. She knew the answer immediately! The block of ice turned to vapor so quickly that the expansion caused the explosion. When water turns from a liquid to a gas the volume increases (We looked it up) by 1096 times. (Thanks to Physicist Robert Muller of UCB, I remembered it was about 1000 times.) So mystery solved.

The Tunguska meteorite blew up for possibly similar reasons, Comets are really just dirty snowballs. The change to gas caused by the intense heating may have caused it to explode. Just like the block of ice on Mythbusters. This is apparently the conclusion Michael Kelley reaches in his soon to be published paper.

Time after time in science, an observation or a strange occurrence will lead to such interesting explanations. That’s why I so avidly support Science education. I want today’s kids to experience and appreciate the giddy wonder of how the Universe works!

Note: After writing this I discovered a story on space.com about it. The original story that caught Daniel’s eye was in National Geographic. They did not talk enough about the Meteor versus comet though!