Image Credit: Don Davis / NASA
Well, first, we can stop and take a deep breath, because we are not going to be killed by an asteroid tonight. Or tomorrow. Or, most likely, any time in the next several million years. So, since we have some time to spare, let's look at the real story behind yesterday and today's flurry of stories on NASA's beleaguered asteroid hunt.
In 2005, Congress mandated that NASA discover 90% of all asteroids larger than 140 meters (150 yards) in diameter that could threaten the Earth, and they set a deadline of 2020. Since then, several major surveys have been looking for asteroids, including the Catalina Sky Survey, Spacewatch, and the Lincoln Near Earth Asteroid Research program (more are listed here). These surveys have discovered over 6200 potentially dangerous asteroids. Out of all of those, only one has been found to be on a collision course with Earth. That tiny asteroid, called 2008 TC3, hit the Sudanese desert last October, causing no damage and dropping several pounds of meteorites on the desert.
Last year, Congress asked for an update on NASA's search for potentially dangerous asteroids. In a bit of, um, interesting timing, that report came out this week, just after the impact of an unknown rock into the planet Jupiter and the impact of some other unknown thing with Saturn's rings. You can read the report here; it's great for insomnia.
The gist of the report is that the near-Earth asteroid searches are going well, but that there isn't enough money to finish the search by the Congress-mandated date of 2020. The report also suggests that some money be invested in a new telescope or two, some additional staffing, and maybe even a space mission. Again, that is if we want to finish the search by 2020. At current funding levels, the search will proceed, but at a slower pace. But, since Congress mandated the 2020 deadline, and astronomers won't be able to meet them with current funding, there's a problem.
The one thing that almost certainly isn't a problem is whether a delay in completing the search could result in a disaster for humans, with an unseen asteroid creeping up and ending civilization as we know it. This is highly unlikely. We think we've found most of the large asteroids (that can do the most damage) -- these are rare, and relatively easy to see because they are big. It's the smaller ones capable of wiping out several hundred square miles (city-sized areas) that are hard to find, and we probably have a long way to go before we find all of these -- they are hard to see, and there are probably tens of thousands of them yet to be found. But despite there being so many of these small asteroids, the chances of one of these asteroids hitting the Earth in the next few decades is very tiny -- outer space is much bigger than most people realize, and the Earth much smaller than we think.
In short, we are not endangering ourselves if it takes longer than 2020 to find all the potentially-hazardous asteroids larger than 140 meters in diameter. The facts that we are funding the search, even if at a minimal level and that we are even looking for potentially hazardous asteroids (no other country is!) are very encouraging. All the report says is that more money is needed, and if we want to finish in 11 years, we need more funding than has been provided. It's up to NASA, the Obama Administration, and Congress to decide if more funding will be forthcoming. I'm not holding my breath.
EDIT: While reading through more of the released report, I came across this graph showing the expected fraction of near-Earth asteroids that would be found without increased funding (lower dashed line) and with increased funding from various upcoming and proposed telescopes and space missions. In short, additional funding meets the goal, at current levels we don't come close but do make progress.
Image Credit: Lindley Johnson, NASA, “Near Earth Object Program” presentation to the Committee to Review Near-EarthObject Surveys and Hazard Mitigation Strategies, December 9, 2008.