Stories tagged asteroid

The flyby of asteroid 2012 DA14 on Feb. 15, 2013, will be the closest known approach to Earth for an object its size, but there is no chance it will hit Earth.

Jun
23
2010

So, this spacecraft that was launched over seven years ago to collect a sample off an asteroid is back? I didn't even know it had left! I am way out of the loop on the activities of the Japan Aerospace Exploration Agency (JAXA) and if this mission is any example, they are doing some sweet stuff.

A Light in the Sky: Hayabusa streaked across the sky through the clouds as it re-entered Earth’s atmosphere over the Woomera Test Range in Australia. In Kingoonya, the spacecraft’s re-entry was visible to the human eye for 15 seconds.
A Light in the Sky: Hayabusa streaked across the sky through the clouds as it re-entered Earth’s atmosphere over the Woomera Test Range in Australia. In Kingoonya, the spacecraft’s re-entry was visible to the human eye for 15 seconds.Courtesy NASA/Ed Schilling
was launched on May 9, 2003 with the intent of it flying to an asteroid, photographing the bejesus out of it, then "landing" on it, collecting a sample and finally returning to Earth. And it did make it to the asteroid and back - returning to Earth on the 13th of June.

Hayabusa did have some troubles along the way – losing a miniprobe to deep space, the failure of two reaction wheels, the failure to properly land and collect a sample (though a sample may still have been obtained)… It was not a flawless mission, but to achieve what they did is no small feat - pretty amazing if you ask me.

Here are some links to learn more.
The JAXA main site.
Hayabusa JAXA mission page.

Apr
30
2009

Killer asteroid?: Artist conception of impact event
Killer asteroid?: Artist conception of impact eventCourtesy NASA
The old “What really killed the dinosaurs” controversy is back in the news. And once again, it’s Princeton geophysicist Gerta Keller stirring up the pot.

Death from above?: Perhaps not.
Death from above?: Perhaps not.Courtesy Mark Ryan
Keller and her colleague Thierry Adatte of the University of Lausanne in Switzerland have published yet another paper challenging the prevailing theory that an asteroid was the major cause of the extinction of the dinosaurs at the end of the Cretaceous Period 65 million years ago. The extinction affected over 60 percent of animal species including all of the non-avian dinosaurs.

Actually a number of events were occurring around the end of the Cretaceous including long-term volcanic activity, rapid marine regression, and the infamous asteroid impact. There’s also evidence that some of the dinosaur population was already in decline 10 million years prior to the events. But the scenario is usually played out with the meteor coming late in the sequence and delivering the deathblow to an already weakened eco-system, and paving the way for mammals to take over the ecological gap.

K-T boundary layer: The Cretaceous-Tertiary boundary layer located near Trinidad, Colorado. The pale-gray 1-inch iridium layer (arrow) is sandwiched between coal layers and contains shocked quartz and other evidence of a large asteroid impact. The scale bar is 6 inches in length.
K-T boundary layer: The Cretaceous-Tertiary boundary layer located near Trinidad, Colorado. The pale-gray 1-inch iridium layer (arrow) is sandwiched between coal layers and contains shocked quartz and other evidence of a large asteroid impact. The scale bar is 6 inches in length.Courtesy Mark Ryan
The asteroid impact hypothesis was first proposed in 1980 by Luis Alvarez of the University of California after he and his son Walter discovered a claystone layer rich in the rare-earth element iridium and peppered with shocked quartz in many locations around the world. Iridium is a rare element not commonly found on the Earth’s surface but abundant in meteorites. Shocked quartz was first noticed in sand grains in craters created by nuclear test bombs and later in meteor impact sites. Alvarez hypothesized that the only other possible source for this naturally deposited strata would be from a large extraterrestrial object hitting the Earth. From studying the amount of iridium found in Cretaceous-Tertiary (K-T) boundary formations, he calculated that a bolide about 6 miles across would have been necessary to create that much iridium around the world. But at the time evidence of such an was unknown. It wasn’t until after Luis Alvarez’s death in 1988 that a crater on the Yucatan Peninsula near Chicxulub Mexico became the chief suspect. The Chicxulub impact crater was the right size and the right age fitting all the criteria of a Cretaceous extinction event.

But Keller claims the asteroid came too early to put the coup de grace on dinosaurs or any species for that matter. Her study of spherules in strata at localities in Mexico has convinced her that the asteroid collided with Earth 300,000 years before any mass extinction.

At El Penon, a location very near the impact crater site, Keller and Adatte studied a 30-ft layer of sandstone above the iridium layer that they calculated had been laid down at a rate of about 1-inch per thousand years. This means it took 300,000 years to pile up the entire section of sediment.

Fossils were analyzed on either side of the iridium layer and the researchers found that of 52 species counted below the iridium layer (meaning before the impact), the same 52 species were found above it, meaning the asteroid hadn’t caused any extinction. But at the top of the 30 feet of sandstone overlaying the iridium claystone things were different.

"The mass extinction level can be seen above this interval," Keller says. "Not a single species went extinct as a result of the Chicxulub impact."

The more likely culprit, according to Keller, is India’s Deccan Traps flood basalts which for several million years poured out tremendous amounts of lava and noxious fumes into the atmosphere that would have had put long and tremendous stress on the existing ecosystem. Keller seems to roll out a paper on the subject every year or so in the last decade. We covered some of her Deccan Traps research 2007 which you can read here.

Whatever the case we do know is that non-avian dinosaurs left the planet after the Cretaceous, as none of their fossils have been found above the K-T Boundary. Well, even that doesn’t appear to be the case anymore. Recent dinosaur fossils found in the San Juan Basin in northwestern New Mexico are suspected to come from a stratum that post-dates the Cretaceous extinction. More research needs to be done on the find, but even this wouldn’t be unexpected. Even after the host declares the party’s over, there are always some stragglers who just don’t want to leave.

Keller's paper was published this week in the Journal of the Geological Society.

MORE LINKS
ScienceDaily story
What Killed the Dinosaurs?
Gerta Keller's Chicxulub Debate
Dinosaur Killer May Have Been Volcanism

Mar
05
2009

When I stumble across stories like this one about a space rock that made a close approach to Earth on Monday, I can't help but think that maybe all the bad news we've been hearing lately is not so bad after all. Sure, the economy is in shambles and everyone seems a little down on their luck, but it could be a lot worse, right? An asteroid could explode over your house with the force of 1,000 atomic bombs, much like the one that fell on Siberia just 100 years ago in something known as the Tunguska event.

Luckily this didn't happen on Monday. The asteroid known as 2009 DD45 was spotted just days earlier by scientists at the Siding Spring Observatory in Australia, and on Monday it sailed by at about 49,000 miles from Earth. Phew!

If you're like me, you might be asking yourself why this wasn't front page news? One answer is that researchers only discovered the asteroid in late February, and according to astrophysicist Timothy Spahr from the Harvard-Smithsonian Center for Astrophysics, they knew within hours that it posed no threat to Earth.

2009 DD45 is just one of many near-Earth objects that researchers are keeping close tabs on. In 1999 a rating system was developed to categorize the threat of asteroids and comets called the Torino Rating Scale. On NASA's website you can see a chart of recent and upcoming "close approaches" of asteroids being tracked by researchers from around the world. There are more than you might think, but most of them are very low on the Torino scale, which means scientists predict that they pose no real threat to Earth.

Still, this brings up a good question. If there are so many near-Earth objects out there, and if we know that the Earth has been hit by asteroids many times before, is this something that we should be worried about? An earlier post on Science Buzz looks at the odds of asteroid impact. What do you think?

You can read a recent document by the United Nations Working Group on Near-Earth Objects to see how scientists and governments are working to define policies related to asteroids and the threats that they pose.

Today is the 100th anniversary of the Tunguska event, a massive explosion in remote Siberia which flattened trees for miles around. To this day no one is quite sure what it was, though the leading candidates are a collision with a large meteorite or a small asteroid. You can learn more about the event here.


Stardust Capsule: Image courtesy NASA.
From Lawrence Livermore National Laboratory:

Contrary to expectations for a small icy body, much of the comet dust returned by the Stardust mission formed very close to the young sun and was altered from the solar system’s early materials.

When the Stardust mission returned to Earth with samples from the comet Wild 2 in 2006, scientists knew the material would provide new clues about the formation of our solar system, but they didn’t know exactly how.

New research by scientists at Lawrence Livermore National Laboratory and collaborators reveals that, in addition to containing material that formed very close to the young sun, the dust from Wild 2 also is missing ingredients that would be expected in comet dust. Surprisingly, the Wild 2 comet sample better resembles a meteorite from the asteroid belt rather than an ancient, unaltered comet.

More on this story here.

More on the Stardust/Wild 2 mission here.

Big rocks hurtling through space tend to smash into our planet. Unfortunately if these rocks are big enough they could easily wipe out human civilization. So now the United Nations is drafting a plan about how to respond to an eminent asteroid impact. And no, their first step is not to hire Bruce Willis.

Jan
14
2007

Near Earth Objects (NEOs) are plentifull.

Asteroid hit.: Artist: Don Davis
Asteroid hit.: Artist: Don Davis
If a person lives to be 80, her or his odds of being around when the next multi-megaton blast from an asteroid collision occurs (somewhere on the planet) are roughly 1 in 12.5. Space within Earth's orbit is crowded with Near Earth Objects. Here is a link to a video of the movement of hundreds of NEO's (400 days).

Some recent near misses

  • On March 18, 2004, Asteroid 2004 FH passed approximately 26,500 miles above the Earth's surface (one-tenth of the distance to the Moon). Astronomers had detected it just three days before.
  • Another near earth object designated 2004 AS1 created concern on Jan 13, 2004. Initial measurements indicated that it would hit Earth within 27 hours. "Astronomers come within minutes of alerting the world to a possible asteroid strike." Wired News
  • Near Earth Asteroid 2004 MN4, briefly held a Torino Scale index of 4 (a record high) before being declared safe.


Near miss: Asteroid 2004 FH's flyby (NASA/JPL)

More Near Earth Object links

NASA impact risk assessment FAQ.
Armagh Observatory information.
NASA NEO basics. page
NASA images.