|The dinosaurs were the dominant species—until an asteroid slammed into the Yucatan 65 million years ago and wiped their habitat out. We don't want to be next dinosaurs. That's why the B612 Foundation is building Sentinel.
We Don’t Have to Play Cosmic Russian Roulette With Asteroids Anymore from Singularity University tells us:
In the grand scheme, impacts are pretty common. Impacts like the Tunguska event in 1908 when a suspected asteroid flattened 1,000 square miles of forest in Siberia. Or last year, when a smaller asteroid detonated with a force equivalent to some 440 kilotons of TNT over the city of Chelyabinsk, Russia shattering windows and frightening residents.
In the last decade, the Nuclear Test Ban Treaty system to detect atmospheric nuclear weapons tests hasn't heard a single bomb blast—but it's recorded scores of asteroid explosions. B612 made an animation of 26 of these from 1 to 600 kilotons. (The atomic bomb that destroyed Hiroshima in 1945 was 15 kilotons.)
Most of these events were too high to do serious damage, but they show how often near-Earth asteroids hit. Tunguska was a multi-megaton blast, bigger than the most powerful atomic bombs in existence. Tunguska was a hundred-year event, and there's a 1% chance of a bigger 100-megaton impact in our lifetime (or 0.01% in any given year).
But when it comes to guarding against an asteroid that could level an entire city or more, Lu says, we're trusting to dumb luck. "The first notice you get is a flash in the sky and a sonic boom." How'd NASA learn about Chelyabinsk? Twitter.
Though Sentinel will focus on larger, more dangerous asteroids, it will also detect some Chelyabinsk-sized objects. And NASA's upcoming ATLAS system of small telescopes will provide advance warning for some (but not all) such strikes, so folks can evacuate or at least stay away from windows.
Even so, there's yet a lot more work to be done.
Scientists have only cataloged about 10,000 or 1% of all near-Earth asteroids. It's estimated we've mapped about 90% of the biggest, extinction-level threats. But 10% are missing in action, and we know nothing of the million or so smaller but still immensely destructive asteroids that could take out an area the size of a state or city.
At the current pace, it would take a thousand years to find them all.
Part of the problem is that the telescopes on the ground or in Earth orbit have a limited view. And asteroids are the color of charcoal. The proverbial needle in a haystack—only the needle is black, the hay is black, and the stack is the size of the inner solar system.
There's a relatively straightforward solution, however. Station a telescope near the orbit of Venus to expand its view, turn away from the glare of the sun, and look in the infrared, where the heat of an otherwise dark asteroid makes it easier to spot.
This is precisely the strategy behind B612s $450-million Sentinel telescope. The project is well underway and boasts a talented roster of deep space mission veterans. Ball Aerospace, the firm behind the Kepler Space Telescope and the optics in the James Webb Space Telescope (among other projects including Hubble), will build Sentinel.
Lu says the project's firmly in the "screw level" phase, and raising additional funds—the nonprofit depends on philanthropic contributions—is the most urgent need.
Provided all goes to plan, Sentinel will launch on a SpaceX Falcon 9 rocket in 2018. The telescope will assume a Venus-like orbit and, looking back to Earth orbit, make repeated infrared observations of the sky in search of moving objects. The data will be sent to Earth, compiled in a public database, and used to calculate asteroid orbits.
According to B612, Sentinel could find over 20,000 new asteroids in its first month—more than all those found in the 30 years we've been looking. Over its 6.5-year mission (and it could be longer), the team believes they'll discover and catalog 90% of all asteroids bigger than 140 meters and many smaller asteroids down to 30 meters.B612 is confident it can raise the funds to send Sentinel into space. Let's hope humanity proves itself more intelligent than the dinosaurs, for if we don't, we simply don't deserve a fate better than theirs.
Wednesday, July 02, 2014
We Can See What the Dinosaurs Could Not
Posted by Unknown at 19:00