TALK about a near miss. Next week the Canadian Space Agency (CSA) will launch the world鈥檚 first dedicated asteroid-hunting satellite 鈥� just after one of the hottest events in space rock history: a surprise meteor that exploded over Russia on 15 February.
The Canadian telescope has been years in the making, so it is pure chance that it will blast off hard on the heels of that big event. But the meteor, paired with a close fly-by of asteroid 2012 DA14 on the same day, has whetted the appetite of government and privately funded rock-watchers.
鈥淚t was quite the coincidence, but also quite the wake-up call, to have these two asteroid events back to back,鈥� says Peter Diamandis, co-founder of the commercial asteroid mining firm Planetary Resources.
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The meteor that blew apart over Russia was probably around 17 metres wide, making it the largest object to enter Earth鈥檚 atmosphere since 1908. It caused a 470-kiloton blast, and the resulting shock wave shattered glass, damaged 3000 buildings and injured nearly 1500 people in the Chelyabinsk region.
Researchers at Ural State University in Yekaterinburg say they have from Lake Chebarkul and determined that they are ordinary chondrites. Although this is the most common type of rock in space, such meteorites look a lot like terrestrial rocks, so they are difficult to recognise and rarely collected. The Chebarkul meteorite, if verified, will be a handy addition to the scientific catalogue (see 鈥�Mining meteorites for Earth鈥檚 history鈥�).
Meanwhile, at 45 metres wide, 2012 DA14 could have caused even greater destruction, had it not swooped by well above Earth鈥檚 surface. So how did we see one harmless asteroid coming and miss another that created havoc?
Astronomers believe they have identified more than 90 per cent of the truly devastating asteroids around the size of the one that killed the dinosaurs. We know nothing about most of the smaller rocks that are capable of wrecking cities (see graph). Luckily Canada鈥檚 , or NEOSSat, should start filling in the gaps when it launches on 25 February, says CSA鈥檚 Denis Laurin.
About the size of a suitcase, NEOSSat鈥檚 lofty position in space should allow it to spot asteroids headed our way during the day, when they would otherwise disappear in the glare of the sun. This fills in a blind spot for ground-based observatories. The Russian meteor was a daytime arrival, although it was too small for NEOSSat to have detected, says Laurin. Instead, the satellite will search for and catalogue the thousands of asteroids larger than 500 metres that we think are zooming around unnoticed.
The private space industry also wants to get in on the act. Planetary Resources鈥� Diamandis says he has received a number of emails from people keen to invest after seeing reports of the Russian impact. The company鈥檚 Arkyd-100 space telescope, due to launch in two years, is designed to hunt for potentially profitable space rocks, but it will also be able to spot any on a collision course with Earth.
A future round of telescopes will have propulsion systems, so they could even divert rocks heading our way. Planetary Resources will do this for free. 鈥淲e鈥檙e not going to be charging extortion money to protect the Earth,鈥� says Diamandis.
鈥淲e鈥檙e a commercial firm, but we鈥檙e not going to be charging extortion money to protect the Earth鈥�
The non-profit in California is also raising money for its Sentinel space telescope, due for launch in 2018. It is expected to map more than 90 per cent of asteroids larger than 100 metres and more than 50 per cent of ones like 2012 DA14. The mission should even be able to spot a good number of objects similar in size to the Russian meteor, says chairman Ed Lu.
Like Planetary Resources, B612 has seen a flurry of interest and a surge in donations since the Russian blast. 鈥淚n some sense this was a great warning, because while there were injuries, it wasn鈥檛 that bad,鈥� says Lu.
An asteroid big enough to level a city should hit Earth once every 2000 years, but the odds of one actually striking a city are very small. Still, such an event should be easy to predict and prevent with current technology, he says. 鈥淚 feel a bit like the people in New Orleans who said the levee should be fixed before Katrina,鈥� says Lu. 鈥淎fter Katrina, everyone realised maybe we should have listened.鈥�
Mining meteorites for Earth鈥檚 history
Once they land on Earth, meteorites change status from threat to scientific bounty. 鈥淭hey are in-hand samples of the original building blocks of our planets,鈥� says William Bottke of the Southwest Research Institute in Boulder, Colorado.
Even as news of the Russian meteor broke, Sam Kounaves of Tufts University in Medford, Massachusetts, was presenting analysis of a Martian meteorite collected in 1979. That space rock hints the surface of Mars is riddled with chemicals related to household bleach, says Kounaves, who spoke on 15 February at a scientific meeting in Boston. The find increases the odds that carbon-bearing compounds called organics 鈥� strong indicators of life 鈥� may have been broken down by reactive chemicals, and suggests that we need to dig deeper to search for traces of past life on Mars.
Another space rock that fell in northern California in 2012 put a wrinkle in the theory that asteroids delivered organics to Earth and other worlds. Videos, photos and radar data allowed scientists to reconstruct its trajectory, letting them quickly gather fresh fragments that turned out to be oddly low in organics.
A meteorite that was tracked until it landed in Sudan in 2008 turned out to be from an asteroid that had partly melted, like a planet. Now scientists will be eager to get results from the Russian meteorite, to see what secrets of the solar system it may reveal.
Lisa Grossman
This article appeared in print under the headline 鈥淎steroid sentinels to stand guard in sky鈥�
