Wednesday, October 6, 2010

Asteroid Double Header

The Lemming has two articles about asteroids: one of more theoretical interest, the other a rather practical matter.

Lutetia: a Dusty Gray Asteroid

"Huge Asteroid Wrapped in Thick Dust Blanket" (October 5, 2010)

"If astronauts ever visit the asteroid Lutetia, they may have to strap on snowshoes to avoid sinking into its nearly half-mile-thick layer of dust.

"Dusty debris shrouds the huge asteroid to a depth of at least 2,000 feet (600 meters), scientists have calculated. The dust probably resembles the regolith found on the moon, and it's a result of the intense cosmic pummeling Lutetia has endured from other space rocks since the birth of the solar system.

" 'It must have been produced by impacts,' said Rita Schulz of the European Space Agency in a media briefing yesterday (Oct. 4) in Pasadena, Calif. The announcement came at a conference organized by the American Astronomical Society's Division of Planetary Sciences..."

An article about a dusty asteroid may seem too theoretical to be interesting: pretty dry stuff.

The new photos are from the European Space Agency's (ESA) Rosetta spacecraft and were taken during a flyby in July. Other data gathered shows that Lutetia is denser that it should be, if it was dust and rubble all the way through. That suggests that it's got a more-or-less-solid core.

So, why be interested in some asteroid between the orbits of Mars and Jupiter? We can't eat it, or use it to watch the Super Bowl, so why bother?

An answer to the "so what" question depends on what a person finds interesting. For some, including the Lemming, Lutetia sounds like a fascinating place. Not ideal vacation real estate, maybe, but quite interesting in other ways. Like someone said, describing the asteroid's color:

"...'It is boringly gray,' [ESA's Rita] Schulz said. But that doesn't mean the asteroid is any less interesting, she added. 'That means it's like the moon, which isn't boring at all.'..."

It's all in how you look at the universe.

It's the Small Ones You Need to Worry About

"Forget Big Asteroids: It's the Smaller Rocks That Sneak In and Blow Up "
Leonard David, (October 5, 2010)

"Put aside the vision of Bruce Willis wrestling with huge space rocks threatening to doom Earth 'Armageddon'-style. It turns out that people should be more worried about smaller space rocks that explode in our atmosphere.

"While smaller than Earth-busting asteroids, these "airbursters" — like the space rock that exploded in 1908 high over Tunguska, Siberia — are more immediate threats, scientists say. They can cause localized destruction and may intrude in our airspace with little warning time.

"When an airbursting asteroid, called a bolide, exploded over an island region of Indonesia late last year, it rocked the residents' world with an estimated energy release of about 50 kilotons, equal to some 110,000 pounds of TNT...."

Oh, come on: how often does something with the destructive potential of a tactical nuke hit Earth?

Fairly often, it turns out:

"...Such objects are expected to impact the Earth on average every two to 12 years...."

Earlier this year I described what would most likely happen if a larger rock, the sort that comes down every 11 centuries or so, went off over Dallas, Texas. (May 2, 2010) It wouldn't, in the Lemming's opinion, bring about the downfall of Western civilization: but there'd be really sharp decrease in property values in and around Dallas.

The sort of event this article discusses is something along the lines of what happened over Tunguska about 102 years ago. (September 14, 2009) That killed quite a few reindeer - and at least one man who was too close. (Planetary Science Institute)

Comparison Time

Thanks to generations of education and reminders in news and other media, most folks living in the English-speaking world know about the nuclear bomb that went off over Hiroshima. Depending on who you listen to, the Hiroshima atomic explosion's force was between 13 and 18 kilotons. And the Lemming knows: war isn't nice. (Another War-on-Terror Blog (October 16, 2009))

Let's say that the Hiroshima bomb was at the top end of that range: 18 kilotons. The bolide that went off over Indonesia had a yield of around 50 kilotons. A tad over 2¾ times the force of the Hiroshima explosion. Happily, it went off over water - and possibly high enough so that effects on the surface weren't all that catastrophic.

A 50 kiloton explosion over, say, Lisbon, Dehli, Hong Kong, or Lagos? That could be quite unpleasant. Particularly for air traffic.

'We Have the Technology - - -'

The good news is that we've had the technology to detect larger asteroids whose orbits take them near Earth for some time - and have a fair number of them identified. And we most likely have the technology it takes to nudge them away from a collision with our planet.

The bad news is that to date, nobody's gotten to the point of assembling that technology.

The sort-of-good news is that there does seem to be a dawning awareness that there's
  1. A problem
  2. That can be addressed
'Is being' addressed,' as of earlier this year: Bill Text | 111th Congress (2009-2010) | H.R.5587.IH

It's a step in the right direction. The Lemming is pretty sure that other national governments are on the same voyage of discovery. And hopes that somebody's going to have their ducks in a row in time.

The trick now is going to be getting as good at finding and tracking the little stuff as astronomers have gotten with the big rocks.

Related posts:Background:
  • "PLANETARY DEFENSE Department of Defense Cost for the Detection, Exploration, and Rendezvous Mission of Near-Earth Objects"
    Airpower Journal (Summer 1997)
  • "1908 Siberia Explosion" Reconstructing an Asteroid Impact from Eyewitness Accounts"
    Planetary Science Institute (undated)
  • "Tunguska Event"
    earth science australia (undated)

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