NASA’s Wide-field Infrared Survey Explorer (WISE) was launched in December 2009 with the aim of surveying the entire sky for coolest and darkest regions of space in the infrared. Amongst the objects WISE is searching for include near-Earth asteroids and comets. WISE will determine the orbits, size and number of asteroids and comets which will help determine the likelihood of the Earth being a target.
In 2007, William Bottke and collaborators published an article in Nature suggesting that the collisional break-up of the 170-m Baptistina asteroid approximately 160 million years ago produced the Baptistina asteroid family (BAF), and that over time dynamical processes involving the Yarkovsky/YORP effects put some of the BAFs on Earth crossing orbits. Bottke et al. (2007) argued that this shower of asteroids lead to the extinction of the dinosaurs 65 million years ago.
Scientist from the WISE team have now confirmed asteroids from the BAF were not responsible for the extinction. The infrared observations of Near Earth Object WISE project (NEOWISE) are more accurate in determining sizes than previous optical estimates, since the infrared light comes from the asteroid itself while optical light is reflected sunlight and to determine sizes one needs to know about the reflectivity of the object. NEOWISE has already cataloged 157,000 asteroids, including 1,056 members of the BAF. Joseph Masiero and collaborators have determined the original Baptistina asteroid break-up occurred closer to 80 million years ago, which does not allow enough time for the BAF to reach the resonance spot required to fling them towards the Earth. Combining the infrared data with optical data provides a much better estimate of the reflectivity, which the NEOWISE team hopes will help them determine the composition of asteroid belt objects and hence better characterise asteroid family groups.
For more information, see
- Origin of Dinosaur-Killing Asteroid Remains a Mystery, WISE press release
- Main Belt Asteroids with WISE/NEOWISE I: Preliminary Albedos and Diameters, Masiero et al. (2011), ApJ, in press [astro-ph]
- An asteroid breakup 160 Myr ago as the probable source of the K/T impactor, Bottke et al. (2007), Nature, 449, p48 [requires Swinburne login]
- NEOWISE image gallery
[Post by Catarina Ubach & Sarah Maddison]