With a fierce interest in nearby brown dwarfs, I often neglect the significant part of the WISE mission devoted to asteroids. WISE (Wide-Field Infrared Explorer) has catalogued more than 157,000 asteroids in the main belt and discovered 33,000 new objects as part of its NEOWISE activities. Here the benefits of infrared wavelengths become apparent, for we know little about the reflectivity of a given asteroid and thus have trouble figuring out how large it is. Using infrared, WISE can relate light in these frequency ranges to the size and temperature of the object. Having established size, mission scientists can re-calculate the asteroid’s reflectivity.
NEOWISE is actually an enhancement to the WISE data processing system that makes for better detection of moving objects in the WISE data. In addition to the asteroids mentioned above, NEOWISE has also detected more than 500 Near-Earth Objects (NEOs) and roughly 120 comets. We’ve had plentiful studies at visible wavelengths from groups like the Catalina Sky Survey, Spacewatch and the Near Earth Asteroid Tracking Program, and we’ve also examined some objects with radar, although that requires the objects to pass fairly close to the Earth. Thus we have uncovered plenty of objects, including some 7600 NEOs and hundreds of thousands of main belt asteroids, but have been able to physically characterize only a small number of them.
NEOWISE begins to bridge this gap, and along the way is uncovering information about the so-called ‘dinosaur killer’ asteroid, once thought to be associated with the object known as (298) Baptistina. It was back in 2007 that Baptistina was suggested as the source of the object that struck the Earth in the Cretaceous/Tertiary extinction event 65.5 million years ago, contributing to the demise of the dinosaurs. The theory: Baptistina’s parent body, perhaps 170 kilometers in diameter, collided with another 60-kilometer wide asteroid about 160 million years ago, sending a chunk into an Earth-crossing trajectory. Moreover, Baptistina has the characteristics of a carbonaceous chondrite, matching the impactor at Chicxulub crater in the Yucatan.
Image: Scientists think that a giant asteroid, which broke up long ago in the main asteroid belt between Mars and Jupiter, eventually made its way to Earth and led to the extinction of the dinosaurs. Data from NASA’s WISE mission likely rules out the leading suspect, a member of a family of asteroids called Baptistina, so the search for the origins of the dinosaur-killing asteroid goes on. This artist’s concept shows a broken-up asteroid. Credit: NASA/JPL-Caltech.
Call it the ‘Baptistina bombardment,’ a prolonged surge in impact activity that affected both the Earth and the Moon — researchers in 2007 pointed to the prominent crater Tycho as another possible sign of these events. But WISE has now demonstrated, through study of 1,056 members of the Baptistina family, that the parent asteroid broke up much more recently than 160 million years ago, perhaps only 80 million years ago. The question then becomes whether a Baptistina fragment could still have hit the Earth about 15 million years after the collision. Amy Mainzer (JPL), principal investigator of NEOWISE, is co-author of a new paper on the issue:
“This doesn’t give the remnants from the collision very much time to move into a resonance spot, and get flung down to Earth 65 million years ago. This process is thought to normally take many tens of millions of years.”
Mainzer is referring to locations in the main belt where the gravitational forces of the gas giants can nudge asteroids out of their orbits and into a collision course with Earth. And it appears that Baptistina is now in the clear on this charge, with the actual dinosaur killer (if indeed the event was solely precipitated by an asteroid strike, which has not been conclusively proven) remaining unknown. What we do have is plenty of evidence that a 10-kilometer asteroid impacted the Earth 65 million years ago, and we have WISE data that may eventually trace the actual culprit.
The paper suggesting Baptistina’s involvement in the dinosaur extinction event is Bottke et al., “An asteroid breakup 160 Myr ago as the probable source of the K/T impactor,” Nature 449 (September 6, 2007), pp. 48-53 (abstract). And see Larry Klaes’ story Finding the Dino Killer for more background on the original Baptistina theory. The Mainzer paper is Masiero et al., “Main Belt Asteroids with WISE/NEOWISE I: Preliminary Albedos and Diameters,” accepted by the Astrophysical Journal (preprint).
Before WISE meets its demise, any chance it might be used to conduct Optical SETI?
And thanks for linking to my CD article, Paul!
I skimmed the abstracts of the two papers (and Larry’s article) to see if it is explained what the motivation is, if any, to find the culprit asteroid. I wasn’t successful. I understand the need to fully explore the NEO threat today and I understand the science value of asteroid formation and solar system dynamics, but why is it important to locate that one particular asteroid? It is certainly an interesting exercise to test our knowledge but is there more to it than that?
Ron S, my impression regarding the search for the Dino Killer space rock – besides scientific curiousity – was to find out if it was not alone and if any other related objects might do the same to Earth some day.
Dino-Killing Cosmic Impact Wiped Out Ancient Birds, Too
Charles Choi, LiveScience Contributor
Date: 17 September 2011 Time: 02:18 PM ET
Although birds survived the mass extinction that claimed their brethren, the rest of the dinosaurs, birds did not emerge unscathed, scientists now find.
Apparently many ancient lineages of birds died off at the end of the Age of Dinosaurs, researchers added.
Nearly all the modern bird groups, from owls to penguins and so on, began to emerge within 15 million years after the rest of the dinosaurs went extinct.
These birds are subtly but significantly different from many of the ancient lineages that existed before a cosmic impact at the end of the Cretaceous period about 65 million years ago wreaked havoc around the globe.
Full article here:
http://www.livescience.com/16105-cosmic-impact-extinction-archaic-birds.html/
“This doesn’t give the remnants from the collision very much time to move into a resonance spot, and get flung down to Earth …”
Unless the collision occurred near such a spot. Seems to me that resonance spots might be intersected by more than one asteroid, with correspondingly increased chances of collision.
http://www.technologyreview.com/blog/arxiv/27720/
The Amazing Trajectories of Life-Bearing Meteorites from Earth
The asteroid that killed the dinosaurs must have ejected billions of tons of life-bearing rock into space. Now physicists have calculated what must have happened to it.
kfc 04/11/2012
About 65 million years ago, the Earth was struck by an asteroid some 10 km in diameter with a mass of well over a trillion tonnes. We now know the immediate impact of this event—megatsunamis, global wildfires ignited by giant clouds of superheated ash and, of course, the mass extinction of land-based life on Earth.
But in recent years, astrobiologists have begun to study a less well known consequence: the ejection of billions of tons of life-bearing rocks and water into space. By some estimates, the impact could have ejected as much mass as the asteroid itself.
The question that fascinates them is what happened to all this stuff.
Today, we get an answer from Tetsuya Hara and buddies at Kyoto Sangyo University in Japan. These guys say a surprisingly large amount of Earth could have ended up not just on the Moon and Mars, as might be expected, but much further afield.
In particular, they calculate how much would have ended up in other places that seem compatible for life: the Jovian moon Europa, the Saturnian moon Enceladus, and Earth-like exoplanets orbiting other stars.
Their results contain a number of surprises. First, they calculate that almost as much ejecta would have ended up on Europa as on the Moon: around 10^8 individual Earth rocks in some scenarios. That’s because the huge gravitational field around Jupiter acts as a sink for rocks, which then get swept up by the Jovian moons as they orbit.
But perhaps most surprising is the amount that makes its way across interstellar space. Last year, we looked at calculations suggesting that more Earth ejecta must end up in interstellar space than all the other planets combined.
Hara and co go further and estimate how much ought to have made its way to Gliese 581, a red dwarf some 20 light years from here that is thought to have a super-Earth orbiting at the edge of the habitable zone.
They say about a thousand Earth-rocks from this event would have made the trip, taking about a million years to reach their destination.
Of course, nobody knows if microbes can survive that kind of journey or even the shorter trips to Europa and Enceladus. But Hara and buddies say that if microbes can survive that kind of journey, they ought to flourish on a super-Earth in the habitable zone.
That raises another interesting question: how quickly could life-bearing ejecta from Earth (or anywhere else) seed the entire galaxy?
Hara and co calculate that it would take some 10^12 years for ejecta to spread through a volume of space the size of the Milky Way. But since our galaxy is only 10^10 years old, a single ejection event could not have done the trick.
However, they say that if life evolved at 25 different sites in the galaxy 10^10 years ago, then the combined ejecta from these places would now fill the Milky Way.
There’s an interesting corollary to this. If this scenario has indeed taken place, Hara and co say: “then the probability is almost one that our solar system is visited by the microorganisms that originated in extra solar system.”
Entertaining stuff!
Ref: http://arxiv.org/abs/1204.1719: Transfer of Life-Bearing Meteorites from Earth to Other Planets
Volcanoes weakened dino population before asteroid, theory says
A volatile environment rife with volcanic eruptions may have been killing off dinosaurs long before the arrival of the asteroid that wiped out the rest, according to research published in the journal Science. Evidence suggests that huge volcanic eruptions in India caused major climate change and a tough environment for dinosaurs to survive.
In addition, using a precise dating technique on rocks found in Haiti, scientists were able to put the asteroid’s impact at the exact date of the extinction, suggesting that the asteroid was the “coup de grace” for the creatures.
National Geographic News (2/12)
http://news.nationalgeographic.com/news/2013/13/130212–chicxulub-asteroid-dinosaurs-volcano-mass-extinction-environment-science/