The Baptistina family is an asteroid family that was probably produced by the breakup of an asteroid 170 km (110 mi) across 80 million years ago following an impact with a smaller body. The two largest presumed remnants of the parent asteroid are 298 Baptistina and 1696 Nurmela.
The Baptistina family may consist of uncommon carbonaceous chondrite asteroids and meteoroids in similar orbits. Many mountain-sized fragments from the collision would have leaked into the inner solar system through orbital resonances with Mars and Jupiter, causing a prolonged series of asteroid impacts. Previously this collision was believed to have occurred about 160 million years ago, and many impacts between 100 and 50 million years ago were attributed to it. However, new data in 2011 from the Wide-field Infrared Survey Explorer revised the date of the proposed collision which broke up the parent asteroid to about 80 million years ago.
Break-up and suspected impacts
Among the notable asteroid impacts previously attributed to the Baptistina family was the Cretaceous–Paleogene (K–T) impactor; however this is highly unlikely if the new data revising the date of collision of the parent object to 80 million years ago are correct, as it typically takes many tens of millions of years for an asteroid to achieve resonance and collide with an inner planet.  In 2007, it was proposed that chromium concentrations in 66-million-year-old sediment layers at the Cretaceous–Paleogene boundary (K–T boundary) on Earth suggested that the impactor that gouged out Chicxulub Crater belonged to this group. Concerns had been raised regarding the reputed link, in part because very few solid observational constraints exist of the asteroid or family. Indeed, it was recently discovered that 298 Baptistina does not share the same chemical signature as the source of the Cretaceous–Paleogene boundary. It has been speculated that the impactor that produced the lunar crater Tycho 108 million years ago was also a member of the group, although with the revised date of the breakup of the parent body this could not be possible.
In 2011 data from the Wide-field Infrared Survey Explorer revised the date of the proposed collision which broke up the Baptistina parent asteroid to about 80 million years ago. If correct, these data mean it is very unlikely that the K–T impactor was part of this family of asteroids, as it typically takes many tens of millions of years for an asteroid to reach a resonance with Earth and then collide, much more than the 15 million between this breakup and the collision of the K–T impactor. "As a result of the WISE science team's investigation, the demise of the dinosaurs remains in the cold case files," said Lindley Johnson, program executive for the Near Earth Object (NEO) Observation Program.
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- Majaess D., Higgins D., Molnar L., Haegert M., Lane D., Turner D., Nielsen I. (2008). New Constraints on the Asteroid 298 Baptistina, the Alleged Family Member of the K/T Impactor, accepted for publication in the JRASC
- Reddy V., et al. (2008). Composition of 298 Baptistina: Implications for K-T Impactor Link, Asteroids, Comets, Meteors conference.
- "Asteroid didn't do it - so who killed the dinosaurs? NASA rules out Baptistina theory". News.com.au / Fox. 2011. Retrieved 2012-02-29.
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