A little bit of asteroid 1999 RQ36 may wind up on Earth in 2017. That’s assuming that NASA’s OSIRIS mission launches in 2011, with the aim of investigating the properties of such Earth-crossing bodies. And while an asteroid sample may help us understand much about the early Solar System, OSIRIS offers a potentially greater benefit. It can help us sharpen our tracking skills so we can plot asteroid orbits with much greater precision.
How? You’ll recall that we recently discussed the the Yarkovsky Yarkovsky-O’Keefe-Radzievskii-Paddack effect. YORP is the minute push that an asteroid receives over time as it absorbs sunlight and emits heat — let’s call it the Yarkovsky Effect for short. It’s a tricky thing to measure because of the uneven nature of asteroidal surfaces, and the varying wobble and rotation of each. Trying to predict an asteroid’s orbit as it approaches Earth demands that we take the Yarkovsky Effect into account. And OSIRIS is tasked with measuring the effect for the first time.
Without such knowledge, we have no way of determining for sure which of the charted near-Earth objects may emerge as a threat. 1999 RQ36, a little less than 600 meters in diameter, moves within 280,000 miles of Earth, not all that much farther than the distance of the Moon. The International Astronomical Union’s Minor Planet Center calls it ‘potentially hazardous.’ Keep adding up the effects of the Yarkovsky push and that potential could one day be realized.
We’ll know more about OSIRIS’ move through the NASA decision-making process later this year. It’s one of three Discovery-class missions recently selected for study but whether or not it flies depends upon the budget and the demands of competing missions. Whatever the fate of OSIRIS, we need to keep up a persistent effort to convince the powers that be that Earth needs a robust asteroid detection and tracking system, one based both on Earth and in space, and that an asteroid sample return mission has to be part of the package. The issue could not be clearer: the sooner we identify an incoming object, the faster we can deal with it.
Addendum (thanks to Larry Klaes for the tip): Robyn Williams discusses OSIRIS with Michael Drake (University of Arizona), audio and transcript available here.