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NASA raises doubts on asteroid group thought to have killed dinosaurs

Sept. 20, 2011
Courtesy of NASA
and World Science staff


New ev­i­dence sug­gests a family of as­ter­oids re­cently blamed for the de­mise of the di­no­saurs is not the cul­prit, NASA sci­en­tists say, keep­ing the case open on one of Earth’s great mys­ter­ies.

While many sci­en­tists agree that a large as­ter­oid crashed in­to Earth about 65 mil­lion years ago, kill­ing off the giant rep­tiles and some oth­er life forms, they don’t know ex­actly where that ob­ject came from or how it got he­re. 

Artist's con­cept of the Wide-field In­fra­red Sur­vey Ex­plor­er. (Cred­it: NA­SA/JPL-Caltech)


A 2007 study us­ing ground-based tele­scopes sug­gested the rem­nant of a huge as­ter­oid, known as Bap­tistina, as a pos­si­ble sus­pect. The study pro­posed that Bap­tistina crashed in­to anoth­er as­ter­oid in the main “as­ter­oid belt” be­tween Mars and Ju­pi­ter about 160 mil­lion years ago. The col­li­sion would have sent shat­tered pieces as big as moun­tains fly­ing, one of which hit Earth.

But new ob­serva­t­ions from NASA’s Wide-field In­fra­red Sur­vey Ex­plor­er (WISE) sat­el­lite may rule out the Bap­tistina con­nec­tion, ac­cord­ing to the agen­cy’s re­search­ers. This bol­sters oth­er re­cent ev­i­dence ex­on­er­at­ing the fam­i­ly, they add.

“The orig­i­nal cal­cula­t­ions with vis­i­ble light es­ti­mat­ed the size and re­flec­ti­vity of the Bap­tistina family mem­bers, lead­ing to es­ti­mates of their age, but we now know those es­ti­mates were off. With in­fra­red light, WISE was able to get a more ac­cu­rate es­ti­mate, which throws the tim­ing of the Bap­tistina the­o­ry in­to ques­tion,” said Lind­ley John­son, pro­gram ex­ec­u­tive for the Near Earth Ob­ject Ob­serva­t­ion Pro­gram at NASA Head­quar­ters in Wash­ing­ton.

“The de­mise of the di­no­saurs re­mains in the cold case files.”

The sat­el­lite sur­veyed the sky twice in in­fra­red light from Jan­u­ary 2010 to Feb­ru­ary 2011. The as­ter­oid-hunting por­tion of the mis­sion used the da­ta to cat­a­logue more than 157,000 as­ter­oids in the main belt and dis­cov­ered more than 33,000 new ones.

Vis­i­ble light re­flects off an as­ter­oid. With­out know­ing how re­flec­tive the sur­face of the as­ter­oid is, it’s hard to ac­cu­rately es­tab­lish size. In­fra­red light ob­serva­t­ions al­low a more ac­cu­rate size es­ti­mate. They de­tect in­fra­red light com­ing from the as­ter­oid it­self, which helps re­veal its tem­per­a­ture and size. Once the size is known, the ob­ject’s re­flec­ti­vity can be re-cal­culated by com­bin­ing in­fra­red with vis­i­ble-light da­ta.

The NASA in­ves­ti­ga­tors meas­ured the re­flec­ti­vity and the size of about 120,000 as­ter­oids in the main belt, in­clud­ing 1,056 mem­bers of the Bap­tistina fam­i­ly. The sci­en­tists cal­culated the orig­i­nal par­ent Bap­tistina as­ter­oid ac­tu­ally broke up clos­er to 80 mil­lion years ago, half as long as orig­i­nally pro­posed. That would­n’t leave enough time for the as­ter­oid to get he­re, they pro­posed.

This cal­cula­t­ion was pos­si­ble be­cause the size and re­flec­ti­vity of the as­ter­oid family mem­bers in­di­cate how much time would have been re­quired to reach their cur­rent loca­t­ion­s—larger as­ter­oids would not dis­perse in their or­bits as fast as smaller ones.


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New evidence suggests a family of asteroids recently blamed for the demise of the dinosaurs is not the culprit, NASA scientists say, keeping the case open on one of Earth’s great mysteries. While many scientists agree that a large asteroid crashed into Earth about 65 million years ago, killing off the dinosaurs and some other lifeforms, they don’t know exactly where that object came from or how it got here. A 2007 study using ground-based telescopes suggested the remnant of a huge asteroid, known as Baptistina, as a possible suspect. According to that theory, Baptistina crashed into another asteroid in the main belt between Mars and Jupiter about 160 million years ago. The collision would have sent shattered pieces as big as mountains flying, one of which hit Earth. But new observations from NASA’s Wide-field Infrared Survey Explorer (WISE) satellite may rule out the Baptistina connection, according to the agency’s researchers. This bolsters other recent evidence exonerating the family, they add. “The original calculations with visible light estimated the size and reflectivity of the Baptistina family members, leading to estimates of their age, but we now know those estimates were off. With infrared light, WISE was able to get a more accurate estimate, which throws the timing of the Baptistina theory into question,” said Lindley Johnson, program executive for the Near Earth Object Observation Program at NASA Headquarters in Washington. “The demise of the dinosaurs remains in the cold case files.” The satellite surveyed the sky twice in infrared light from January 2010 to February 2011. The asteroid-hunting portion of the mission used the data to catalogue more than 157,000 asteroids in the main belt and discovered more than 33,000 new ones. Visible light reflects off an asteroid. Without knowing how reflective the surface of the asteroid is, it’s hard to accurately establish size. Infrared light observations allow a more accurate size estimate. They detect infrared light coming from the asteroid itself, which helps reveal its temperature and size. Once the size is known, the object’s reflectivity can be re-calculated by combining infrared with visible-light data. The NASA investigators measured the reflectivity and the size of about 120,000 asteroids in the main belt, including 1,056 members of the Baptistina family. The scientists calculated the original parent Baptistina asteroid actually broke up closer to 80 million years ago, half as long as originally proposed. That wouldn’t leave enough time for the asteroid to get here, they proposed. This calculation was possible because the size and reflectivity of the asteroid family members indicate how much time would have been required to reach their current locations—larger asteroids would not disperse in their orbits as fast as smaller ones. killed dinosaurs