Meteor crater in Arizona, nearly 4,000 feet across and 570 ft. deep, formed by the equivalent of a 10 megaton blast.
The question posed in the header is difficult to answer. However, following the cosmic coincidence of yesterday (meteoroid exploding over Siberia, close passing asteroid DA 14), everyone on the Earth with more than air between the ears ought to be taking potential asteroid (or large meteoroid) strikes, very seriously indeed. (see also: http://www.brane-space.blogspot.com/2013/02/two-cosmic-shots-over-bow-for-earths.html ) Check out also the accompanying image of the Meteor Crater in Arizona (formerly the Barringer Crater) and process its dimensions: 4,000 ft. in diameter (1,200 m) and 570 ft. (170 m) deep.
The crater was was formed by the impact of an iron-nickel meteorite 50 m (165') across, coming in at 28,600 mph, generating an impact energy of 10 megatons. This crater, in other words, would have reduced a city the size of Miramar, FL to rubble. The impact occurred roughly 50,000 years ago. By comparison, the meteoroid that exploded over Russia was about 49 m in diameter, and Russian physicists estimate its explosive release at about 20 Hiroshima bombs of 10 kilotons each, or 200 kilotons - thus, a fifth of a megaton. Small change, in other words.
Meanwhile, a 100- to 130-foot asteroid exploded over
The worst nightmare is the Earth-sterilizing asteroid or planet killer, with explosive equivalent of > 100,000 megatons. This will be from a rock greater than 10km across. While I did write in an earlier blog I would take an asteroid instead of a central meridian solar CME, that only applied to tiny asteroids like DA 14. NOT to planet killers, since a massive CME and planet killer would have the same outcome: most or all of humanity dead or dying.
Astronomer Paul Chodas, who works in NASA's Near-Earth Object program in Pasadena, Calif., decribed the Russian object as:
"....a tiny asteroid. It would be very faint and difficult to detect — not impossible, but difficult."
Meanwhile, the actual asteroid DA 14 2012 that made a heart stopping close pass, was three times the size of the Russian object, and coming in at nearly 40,000 mph. Its blast -energy release was more like a 20 megaton blast.
In many ways then, these things are almost like random terror attacks from the sky. So why aren't more people concerned (up to now, for example, only 12 have read the blog from yesterday, compared to 270 who've read the Dec. 1st blog on the Notre Dame Prep sex video. Can a sex video really be more important or interesting than a potential, obliterating asteroid strike? Wait, don't answer that...
But at least according to Rusty Schweickart, who flew on Apollo 9 in 1969, and helped establish the planet-protecting B612 Foundation (quoted in Saturday's Denver Post referring to Friday's events): "
"After today, a lot of people will be paying attention,"
Well, maybe! If sex or Beyonce don't distract them! Schweickart and his Foundation have been warning NASA for years to put more muscle and money into a heightened asteroid alert. To his credit, he and some former astronauts want to give the world a fighting chance in terms of confronting the specter of an asteroid approach. After all, what good is all our vaunted human intelligence if we meet the same end as the dinosaurs one of these days?
Here's the current skinny: Scientists think there are 500,000 to 1 million "near-Earth" asteroids comparable in size to DA14 or bigger out there. But less than 1 percent have been spotted. Astronomers have catalogued 9,600 of them, of which nearly 1,300 are bigger than 0.6 miles long. That means they are at least of mass extinction level.
Earth's atmosphere gets hit with 100 tons of junk every day, most of it the size of sand and most of it burning up before it reaches the ground, according to NASA. And also, there may be many bolides such as exploded over Siberia, but many will do that over oceans or other areas where few human observers live.
As NASA's Jim Green, director of planetary science, puts it, regarding the Russian event:
"These fireballs happen about once a day or so, but we just don't see them because many of them fall over the ocean or in remote areas. This one was an exception,"
Former Astronaut Schweickart observed:
"The chances of Earth getting hit without warning by one of the big ones are extremely low, so low that it's ridiculous. But the smaller ones are quite different."
This is true, but the probabilities for the monster rocks smacking us ought not be readily dismissed, because one never knows what sort of gravitational perturbations can affect existing orbits. We already know, for example, that an estimated 1,000 asteroids are perturbed from the asteroid belt each year to become Earth-crossers. We call these "Apollo asteroids". We need to keep track of them, because they are the ones that are among the planet killing or mass extinction scales. The smaller ones? Yes, they are nuisances, but we can deal with them if we have some long range planning wherewithal combined with alert observers.
And what are our illustrious politicos doing in the meantime, since the Friday events? Rep. Lamar Smith, R-Texas, chairman of the House Science, Space and Technology Committee called for a hearing in the coming weeks. In his words:
"Today's events are a stark reminder of the need to invest in space science,"
Yes indeed, but we need a lot more than hearings. We need lots more technically-minded people with eyes on the skies.
Schweickart and others meanwhile, have advised that NASA launch a $250 million-a-year program to survey asteroids and work up a deflection plan. The latter would be most effective for the lesser objects but may also help with the larger ones, of at least mass extinction scale. Ideally Russia (especially after Friday) and the USA should combine their resources and work together for the planet's benefit - as opposed to more opportunistic war -making (to ramp up defense budgets), including endless stupid wars on terror.
WTF use is a war on terror, defending against maybe a 'dirty bomb' that can remove a thousand people, when a major meteroid strike - such as produced the Barringer crater- would kill millions, say if it landed directly on New York City? Instead of therefore pumping $200 b a year into wars on terror we ought to be focused on the terror from the skies - which though admitttedly rare- would have consequences that are irreparable.
Schweickart notes that "NASA now has $20 million" for searching out these terrorists in the skies, and adds. ... "It's peanuts."
Sadly, it may well take a monster meteoroid or small asteroid (like DA 14) crashing into a populated area before NASA and other agencies, politicos wake up. That would then be our cosmic 9/11 and prompt us to get off our asses before the really BIG one arrives. Aka, the planet killer!