Thursday, December 31, 2009

Asteroid 99942 Apophis: Radical Waves in 2036?

"Russia May Send Spacecraft to Asteroid"
The Associated Press, via FOXNews (December 30, 2009)

"Russia is considering sending a spacecraft to a large asteroid to knock it off its path and prevent a possible collision with Earth, the head of the country's space agency said Wednesday.

"Anatoly Perminov said the space agency will hold a meeting soon to assess a mission to Apophis, telling Golos Rossii radio that it would invite NASA, the European Space Agency, the Chinese space agency and others to join the project once it is finalized.

"When the 885-foot asteroid was first discovered in 2004, astronomers estimated the chances of it smashing into Earth in its first flyby in 2029 were as high as 1-in-37, but have since lowered their estimate...."

Right now, it's very, very likely that Apophis will miss Earth in 2029. That's the good news. The bad news is that there's a chance that Apophis will pass through a sort of "keyhole" in space near Earth, where Earth's gravity will change it's orbit. The new orbit - if Apophis goes through that very small "keyhole" - would send the asteroid around the sun exactly once every 7/6ths of our years.

If that happens, and it isn't all that likely: Sunday, April 13, 2036, will be a very bad day.

"...If the dice do land the wrong way in 2029, Apophis would have to be deflected by some 5000 miles to miss the Earth in 2036. Hollywood notwithstanding, that's a feat far beyond any current human technology. The fanciful mission in the 1998 movie Armageddon—to drill a hole more than 800 ft. into an asteroid and detonate a nuclear bomb inside it—is about as technically feasible as time travel. In reality, after April 13, 2029, there would be little we could do but plot the precise impact point and start evacuating people...."
(Popular Mechanics)

Mining an Asteroid as Technically Feasible as Time Travel?

I'm inclined to agree that we're not all that close to starting a fairly large mining operation on an asteroid. Not in the next couple decades, anyway.

I wouldn't have compared it to time travel, though: since we've got equipment that can move large quantities of rock, mud, ice, or most other solid or liquid materials right now. Google 'mining equipment manufacturers,' and you'll find quite a list. The trick would be getting the machines to work in a vacuum, and moving them to Apophis.

I think the point Popular Mechanics was trying to make was that if Apophis is going to be moved, the sooner it's done, the more possible it will be.

Dude! 50-Foot Waves?!

If - and it's fairly long odds - Apophis does hit Earth in 2036, it's likely to make quite a splash.

"...According to projections, an Apophis impact would occur somewhere along a curving 30-mile-wide swath stretching across Russia, the Pacific Ocean, Central America and on into the Atlantic. Managua, Nicaragua; San José, Costa Rica; and Caracas, Venezuela, all would be in line for near-direct hits and complete destruction. The most likely target, though, is several thousand miles off the West Coast, where Apophis would create a 5-mile-wide, 9000-ft.-deep 'crater' in the water. The collapse of that transient water crater would trigger tsunamis that would hammer California with an hour-long fusillade of 50-ft. waves...."
(Popular Mechanics)

Again, it's good news / bad news.

The good news would be that surfers on the Pacific coasts would have an hour of really, really big waves.

The bad news is that, in all likelihood, their favorite surf shops wouldn't be around afterward. And neither would the cities they live in.

99942 Apophis: Move It or Break It?

Assuming that it wouldn't be good if Apophis hit Earth, and I think that's a safe assumption: Is nudging it into another orbit the only solution?

That Popular Mechanics article gives the mass of Apophis as 25,000,000 tons. If it came down more-or-less in one piece, that would be very bad. On the other hand, thousands of tons of dust fall on Earth, or are swept up by our planet, every day. Exactly how much seems to be unknown. A rather old article in the Journal of the Royal Astronomical Society of Canada gave estimates on 1,800 or 2,700 tons a day, depending on how fast the dust was moving, on average, relative to Earth. That's dust, mind you: not meteors. But that seems to be at least one of the sources for the "thousands of tons" estimate that other resources say falls on us daily.

Long, short or metric ton? Good question. The estimated dustfall numbers are fairly approximate, anyway, so I'm not going to try to track down which of many "tons" that article referred to.

Let's say it's 2,000 tons of dust/day - year in and year out.

Apophis weighs around 25,000,000 tons. 25,000,000 divided by 2,000 is 12,500. So, if Apophis was blown to bits, but the expanding pile or rubble stayed on a collision course for Earth - we'd have a day where over 10,000 times the usual amount of debris would fall out of the sky.

Depending on how big the pieces were, that could mean trouble for anyone near the impact point: or an incredible light show in the sky. And probably lawsuits from people who were scared or annoyed and figured they ought to sue someone.

Nudging the asteroid out of the way is probably the best idea: but it seems to me that there are alternatives.

And, I'm glad to see that someone on the planet is at least talking about getting ready. Yes: the odds are that Apophis will miss Earth entirely, both times around. But if it turns out to be on a collision course: it would be nice to have something in the planning stages, at least.

Related posts: More:
Update (January 1, 2010)

"Russia May Attack Asteroid That's Virtually No Threat "
Space.com (December 30, 2009)

"Russia is considering a plan to launch a spacecraft capable of moving a huge asteroid in a bid to protect Earth from an impact, but the target space rock poses virtually no threat to our planet and moving it could actually make matters worse, experts say.

"American astronomer Paul Chodas, part of NASA's Near-Earth Object (NEO) Program Office, said Wednesday that claims by a top Russian space official that the asteroid Apophis would definitely crash into Earth around 2036 are inaccurate.

" 'That's not right,' Chodas told SPACE.com. 'The probability of an impact is going down.'

"Anatoly Perminov, chief of Russia's Federal Space Agency, said today that his agency will soon hold a special meeting to discuss a potential mission to Apophis, according to Russian wire reports. Perminov spoke on the Voice of Russia radio and said experts from the United States and other nations and space agencies would be able to join the project once the details are set.

"Perminov said he had heard of Apophis' threat to Earth from a scientist who had calculated that the asteroid was getting closer and would 'surely collide with Earth in the 2030s,' according to Russia's RIA Novosti news service...."

I should probably have included the odds, as stated in the AP article:

"...NASA had put the chances that Apophis could hit Earth in 2036 as 1-in-45,000. In October, after researchers recalculated the asteroid's path, the agency changed its estimate to 1-in-250,000.

"NASA said another close encounter in 2068 will involve a 1-in-330,000 chance of impact...."

odds of 1-in-250,000 - or even 1-in-45,000 - are hardly what I'd use as the basis for saying that something will "surely collide." But then, I'm not with the Russian space program, or RIA Novosti. Maybe the idea of a "sure thing" is different over there?

Or, more reasonably, we're looking at a really effective publicity campaign. Look at if this way: if some hypothetical nation got people believing that they, and only they, were prepared to Save the World from a raging asteroid; and then the predicted time of impact came and went; they'ed be heroes!

Whatever the thought process over there, I'm glad that someone's at least making a sort of test run for asteroid deflection. Sooner or later we'll be looking at something better than 1-in-45,000 odds. Or, rather, in this case: worse.

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