By Laura Matthews: Subscribe to Laura's RSS feed
September 20, 2011 4:24 PM EDT
The Baptistina family of asteroids has just been ruled out in the 65-million year-old cold case surrounding the mysterious death of Earth's dinosaurs, leaving scientists to now ask 'Who did it?'
It is a widely held belief in science that a large asteroid had crashed to Earth some 65 million years ago, taking the lives of dinosaurs and other terrestrial life forms on the planet. But where that asteroid came from and how it found its way to Earth is still unknown by scientists.
Then in 2007, a study conducted using visible-light data from ground-based telescopes made the suggestion that the trace of a huge asteroid known as Baptistina was a possible suspect.
The Baptistina family is an asteroid family likely formed by the breakup of an asteroid 170 kilometers (110 miles) across 80 million years ago. This is following an impact with a smaller body. The largest presumed trace of this parent asteroid is 298 Baptistina.
Scientists believe many mountain-sized fragments from the collision would've leaked into the inner solar system through orbital resonances with Mars and Jupiter, which caused a prolonged series of asteroid impacts between 100 and 50 million years ago. Orbital resonances occur when two orbiting bodies exert a regular, periodic gravitational influence on each other. It greatly enhances the mutual gravitational influence of the bodies, that is, their ability to alter or constrain each other's orbits.
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Simply put, resonances are areas in the main belt where gravity nudges from Jupiter and Saturn can act like a pinball machine that flings asteroids out of the main belt and into the region near Earth.
Scientists believe that one of those pieces may have impacted Earth and cause the dinosaurs' demise.
Not so, says NASA.
In fact, data from the NASA's Wide-field Infrared Survey Explorer (WISE) has revised the date of the proposed collision that destroyed the Baptistina parent to about 80 million years ago. And if this is correct, the data would not only exclude Baptistina as the culprit, but also revise a number of other impacts previously associated with this asteroid family.
WISE is a NASA infrared-wavelength astronomical space telescope launched on Dec. 14, 2009. It was a replacement for the Wide Field Infrared Explorer (WIRE), which had failed within a short time of reaching orbit in March 1999.
WISE is over 1,000 times more sensitive than prior infrared space surveys in certain measurements. It was hibernated on Feb. 17 this year when its transmitter was turned off.
"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 at NASA Headquarters in Washington. "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."
A year of survey
According to NASA, WISE surveyed the entire celestial sky twice in infrared light between January 2010 and February 2011.
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