Update: On February 15, 2013 debris from a disintegrating bolide landed in Chelyabinsk, Russia. Estimates indicate that the bolide was an object of about 15 meters in diameter, on a very shallow entry (approximately 20 degrees), at an impact speed of 18 kilometers/second. To calculate the energy produced and the frequency of such an impact, we assumed (for now) that it is a rock of density 3000 kg/m3 (for dense rock) and entered these values into the Impact Earth! calculator (www.purdue.edu/impactearth) to determine the energy produced (in megatons) and how frequently such an impact might occur. The result is plotted on the Rocks from Space graph shown here. As with the other data points on the graph, this one is based on calculations using best current assumptions. Watch for updates based on revised information as scientists investigate this event.
Results: Energy: 205 kilotons TNT
Average time between impacts: 32.5 years
On February 15, 2013, asteroid 2012 DA14, a 50-meter stony asteroid, will pass the Earth at a distance of about 27,680 kilometers (17,200 miles). Such a close approach happens more frequently than people might think. Objects of this size rarely strike the Earth, however, and 2012 DA14 definitely won’t impact Earth in February. Instead, this close fly-by offers scientists a great chance to study the asteroid.
Ed Beshore, OSIRIS-REx Deputy Principal Investigator, states: “Once again, we are seeing a close pass of a 50-meter-class object. Is something different? Not really -- we are just starting to look more closely and we find that these encounters are indeed common. Impacts have been part of the history of the Earth for billions of years.”
Earth’s history of impacts is evident in craters and other evidence around the world. Scientists document the effects of asteroid impacts, model the relative energy of different impactors, and estimate how frequently objects might impact Earth. The diagram shown here compares the explosive effect and frequency for near-Earth objects the size of 2012 DA14 and 1999 RQ36, the target asteroid of the OSIRIS-REx mission, to the energy and frequency represented by well-known impact events on Earth. [The values shown in the figure below were calculated using the Impact Earth! website, www. purdue.edu/impactearth/.]
Observing campaigns will study the asteroid, 2012 DA14, with various instruments including NASA’s Goldstone radio telescope in California. From these observations, scientists will learn more about its orbit, rotation, and physical characteristics. "NEOs are obviously special because they are hazards to the Earth.” Beshore said. “Over the long term, NEOs either collide with the Sun or a planet, or get thrown from the Solar System by a close gravitational approach. Something is responsible for resupplying the inner Solar System with these objects, and this is the subject of much study. Collision threat aside, NEOs are scientifically interesting — their close approaches to Earth afford excellent opportunities to study them in detail.”
Because of this unique observing opportunity, the OSIRIS-REx Target Asteroids! program includes 2012 DA14 on its list of optimal sample return objects andamateur astronomers involved in this citizen science program plan to have their telescopes trained on 2012 DA14 as it moves rapidly across the sky. Carl Hergenrother, OSIRIS-REx Science Team member and Target Asteroids! coordinator, says, “This object is small and fast but relatively bright – it offers professionals and amateurs a great chance to collect data and test their observing skills. It’s not often that we get to observe such a small asteroid at close range. I will be on the Vatican Advanced Technology Telescope the night of the close approach getting light curve and color observations.”
2012 DA14 is about one-tenth the size of asteroid 1999 RQ36, which the OSIRIS-REx mission will visit in 2018 and from which it will return a sample to Earth in 2023. Astronomers have observed asteroid 1999 RQ36 on close approaches to Earth and obtained data about it as well but the instruments on the OSIRIS-REx spacecraft will relay extremely detailed information about its orbit, rotation, and physical characteristics from just a few meters above the surface. Dante Lauretta, Principal Investigator for the OSIRIS-REx mission, believes 1999 RQ36 may hold important clues to the formation of the solar system. “We believe 1999 RQ36 is a primitive object, relatively unchanged since the beginning of the Solar System. The chance to examine a sample in laboratories here on Earth may lend important clues to the source of organic materials and water — both critical to our understanding of how life arose on Earth, and the prospects for finding it elsewhere. Furthermore, OSIRIS-REx will be a pathfinder, helping us understand the techniques and technologies needed to navigate and work in an asteroid’s microgravity environment— important preparation for dealing with a future hazard or preparing for a human expedition."