In an earlier blog, I talked about the potential risk for wide-area destruction that would occur if an asteroid of sufficient mass collides with Earth. Scientists estimate that there are a very large number of intermediate-sized asteroids that cross Earth’s orbit in their journeys around the Sun, and while many of these so-called “Near Earth Objects” have been identified, most of them (like the one that gave Earth a glancing near-miss and exploded over Chelyabinsk in Russia in 2013) have yet to be detected and are therefore untracked.
There are several proposed methods to circumvent or deflect such an impact if an asteroid is detected soon enough, but the earliest test of one possible way to do so won’t occur until at least 2022 or 2024, and then only if NASA receives Congressional funding for the project. According to the NASA Transition Authorization Act of 2017, that won’t happen until next year’s budget cycle (at best).
The language in NASA’s 2017 approved budget states, in part:
Within a year NASA must provide Congress a report that provides an analysis of possible options that the Administration could employ to divert an object on a likely collision course with Earth.
NASA’s ongoing Near Earth Object Program (NEO) focuses in part on identifying and tracking the category of asteroids larger than 500 feet in diameter, i.e. bigger than a football field. These are described as “city busters” because of the extensive regional damage one of them would cause if it were to impact Earth. NEO has tracked more than 7500 of these objects to date, which represent only about 40% of the estimated total. The Program’s objective is to raise that percentage to 90% over time.
On June 23, NASA responded to that 2017 Congressional directive by proposing a new unmanned space mission they’ve named the Double Asteroid Redirection Test (nicknamed DART, of course, in NASA’s reverse-engineered acronym naming procedure).
DART is actually a pretty cool idea, a non-nuke way to push (or “kick”) the asteroid off course. “Kick” is one of the three options being considered that I mentioned in my earlier blog. The idea here is to slam something into the side of an asteroid that’s headed our way and push it (nudge it?) into a different orbit; one that would prevent it from hitting Earth. NASA calls this “kinetic impact”.
In this test case, NASA will take advantage of a bit of astrodynamic good luck. It happens that an asteroid called Didymos, which is actually a pair of gravity-locked asteroids traveling together, will pass near Earth in 2022, and again in 2024. The larger of the two bodies, Didymos A, is about one-half mile in diameter, and the smaller one, Didymos B, is about 530 feet. Each of these would be considered extremely hazardous if it was to impact Earth.Fortunately, the trajectory of this particular pair will carry them safely away from us, but they present a unique opportunity to test one way to deflect a sizable asteroid from its orbital path. Johns Hopkins University’s Applied Physics Lab will be managing the DART mission. Their website describes the spacecraft mission as follows:
After launch, DART would fly to Didymos and use an APL-developed onboard autonomous targeting system to aim itself at Didymos B. Then the spacecraft would strike the smaller body at a speed about nine times faster than a bullet, approximately 3.7 miles per second. Earth-based observatories would be able to see the impact and the resulting change in the orbit of Didymos B around Didymos A, allowing scientists to better determine the capabilities of kinetic impact as an asteroid mitigation strategy.
In other words, since the two asteroids are gravitationally linked, they’re actually orbiting each other. “Kicking” one of them will affect that orbit, which will allow scientists to measure how effective the DART impact was in moving the smaller asteroid onto a different path.
Take a look at the Johns Hopkins DART website. It even has a video illustrating how the DART mission would play out. As I said, pretty cool, huh?
Only three problems here: NASA’s NEO Program has only identified and tracked 40% of these “city busting” asteroids so far, so if one of the “unidentified” ones comes at us soon, we’re basically sitting ducks. The DART mission is still five years away, and more likely seven, and then it’s only a test to see if the “kick” option works. And Congress won’t get around to actually funding DART until next year.
As I said in an earlier blog, I hope those pesky asteroids agree with our priorities.
Copyright 2017 Dandelion Beach LLC
Cherlyabinsk Image Credit: Tuvix/Youtube
Featured Image: (DART Asteroid after Collision) Copyright European Space Agency (ESA)