SpaceJibe

June 30, 2014

Ancient asteroid destroyer finally found, and it’s a new kind of meteorite

Filed under: Asteroids, Comets, Earth, Inner Solar System, Kuiper Belt, Oort Cloud — bferrari @ 8:56 am

Illustration of a meteor shower.argus/Shutterstock.com

For 50 years, scientists have wondered what annihilated the ancestor of L-chondrites, the roof-smashing, head-bonking meteorites that frequently pummel Earth.

Now, a new kind of meteorite discovered in a southern Sweden limestone quarry may finally solve the mystery, scientists report. The strange new rock may be the missing “other half” from one of the biggest interstellar collisions in a billion years.

“Something we didn’t really know about before was flying around and crashed into the L-chondrites,” said study co-author Gary Huss of the University of Hawaii at Manoa.

The space rock is a 470-million-year-old fossil meteorite first spotted three years ago by workers at Sweden’s Thorsberg quarry, where stonecutters have an expert eye for extraterrestrial objects. Quarriers have plucked 101 fossil meteorites from the pit’s ancient pink limestone in the last two decades. [Photos: New Kind of Meteorite Found in Sweden]

Researchers have nicknamed the new meteorite the “mysterious object” until its formal name is approved, said lead study author Birger Schmitz, of Lund University in Sweden and Chicago’s Field Museum. It will likely be named for a nearby church, the sterplana, he said.

Mysterious find

Geochemically, the meteorite falls into a class called the primitive achondrites, and most resembles a rare group of achondrites called the winonaites. But small differences in certain elements in its chromite grains set the mysterious object apart from the winonaites, and its texture and exposure age distinguish the new meteorite from the other 49,000 or so meteorites found so far on Earth.

“It’s a very, very strange and unusual find,” Schmitz told Live Science’s Our Amazing Planet.

The new meteorite was recently reported online in the journal Earth and Planetary Science Letters, and the study will appear in the journal’s Aug. 15 print edition.

Until now, all of the quarry’s fossil meteorites were L-chondrites. Schmitz, who has led the chondrite cataloging, admitted the rock hunt had become “quite boring.”

But the rare find has not only revitalized interest in the quarry, it has also brought together the world’s top meteorite experts for a global hunt through geologic time. Thanks to Schmitz’s careful detective work on meteorites, scientists now know that each kind of meteorite leaves behind a unique calling card: tough minerals called spinels. Even if meteorites weather away, their spinels linger for hundreds of million of years in Earth rocks. Schmitz and his cohorts think they can pin down how many meteorites rained down on Earth in the past 2.5 billion years, as well as what kind fell, by extracting extraterrestrial spinels from sedimentary rocks. Their work may confirm suspicions that recent meteorite falls represent a mere fraction of the rocks drifting in space.

“I think our new finding adds to the understanding that the meteorites that come down on Earth today may not be entirely representative of what is out there,” Schmitz said. “One thing our study shows is that we maybe don’t know as much as we think we know about the solar system.”

Ancient wreckage

The limestone quarry preserves the remnants of a cosmic cataclysm that took place 470 million years ago, during the Ordovician Period. Scientists think there was an enormous crash between two large bodies out in the asteroid belt. The crash blew apart two asteroids, or an asteroid and comet, slinging dust and debris toward Earth. One of the impactors was the source of all L-chondrite meteorites. But no one has ever found a piece of the rock that hit the L-chondrite parent, until now.

The Swedish meteorite’s exposure age the length of time it sailed through space is the key to placing the fossil space rock at the scene of the crash. The meteorite zipped from the asteroid belt to Earth in just 1 million years. That’s the same remarkably young exposure age as the L-chondrites recovered from the Thorsberg quarry, suggesting the rocks sprayed Earth in the same wave of space debris. [Infographic: Asteroid Belt Explained]

Meteorite expert Tim Swindle, who was not involved in the study, praised the team’s careful analysis and said it was unlikely that any other meteorite but an Ordovician fragment would have such a short exposure age. “Very, very few modern meteorites have exposure ages that low,” said Swindle, a professor at the University of Arizona in Tucson. “Typically, it takes things longer to get here from the asteroid belt,” he said. “It’s a telling argument.”

But because so little is left of the original meteorite almost all its minerals have been altered to clay Swindle thinks there’s wiggle room for linking it to known classes of meteorite, instead of calling it a new find.

“I think it’s entirely plausible [that it's a new kind of meteorite], and it’s a great study, but that’s not a guarantee they’ve got it right,” Swindle said. “But if they didn’t, it’s because of new things we’ll find out in future work, not because of their analysis.”

The geochemical tests were performed on sand-sized chromite spinels, which confirmed the rock’s extraterrestrial origin. The altered clay is also about 100,000 times richer in iridium than terrestrial rocks. Iridium is the element that marks the meteorite impact horizon when the dinosaurs went extinct.

Hunt for space history

Schmitz now plans to search for these strange achondrite spinels in the quarry sediments, as well as in other rocks of the same age around the world. Ordovician meteorite spinels from L-chondrites have been found in China, Russia and Sweden, and small micrometeorites have been discovered in Scotland and South America. Researchers think about 100 times as many meteorites fell on Earth during the Ordovician compared with today, but only about a dozen impact craters of the proper age have been identified. [Crash! 10 Biggest Impact Craters on Earth]

A bigger quest is also in the works. Schmitz and his colleagues plan to dissolve tons of rock in acid in a global search for meteoritic spinel grains. This detective work will help researchers pin down the history of the asteroid belt and solar system. Spinels can provide an estimate of how many meteorites fell in the past, and what kind hit Earth. These tiny pieces of vanished meteorites may fill in missing history, because meteorite impact craters often vanish due to geologic forces.

“This can give you a ground truth for models for how the solar system may have evolved over time,” said Gary Huss, a co-author on the Swedish meteorite study who will collaborate on the spinel search. “I think a lot of people have worried for some time that we don’t really know what’s going on in the asteroid belt.”

Source

October 9, 2013

Meet the asteroid that might hit Earth in 2880

Radar image of 1950 DA acquired by the Arecibo Observatory on March 4, 2001. (NASA/JPL/S. OSTRO)

Radar image of 1950 DA acquired by the Arecibo Observatory on March 4, 2001. (NASA/JPL/S. OSTRO)

There are over 10,000 near-Earth objects (NEOs) that have been identified so far — asteroids and comets of varying sizes that approach the Earth’s orbital distance to within about 28 million miles. Of the 10,000 discoveries, roughly 10 percent are larger than six-tenths of a mile in size — large enough to have disastrous global consequences should one impact the Earth.

This is one of them.

First discovered in February 1950, 1950 DA is a 1.1-kilometer-wide asteroid that was observed for 17 days and then disappeared from view. Then it was spotted again on Dec. 31, 2000 — literally on the eve of the 21st century. Coupled with radar observations made a few weeks later in March 2001 it was found that, along with a rather high rotation rate (2.1 hours), asteroid 1950 DA has a trajectory that will bring it very close to Earth on March 16, 2880. How close? Close enough that, within a specific 20-minute window, a collision can not be entirely ruled out.

Top 10 Ways to Stop an Asteroid

The image above was made from radar observations by the Arecibo Observatory in Puerto Rico in March 2001, when 1950 DA passed within 4.8 million miles of Earth. Is this the mug shot of a future continent-killer?

Radar analysis and research of 1950 DA performed by NASA’s Jet Propulsion Laboratory scientists J.D. Giorgini, S. J. Ostro, Don Yeomans and several others from JPL and other institutions revealed that the impact probability from 1950 DA in March 2880 is, at most, 1 in 300 based on what is known about the asteroid so far.

1 in 300 may sound like a slim chance, but actually this represents a risk 50% greater than that of the average hazard due to all other asteroids from now to then.

However, that’s a maximum value. The study also noted the collision probability for 1950 DA as being in the range from 0 to 0.33%. That upper limit could increase or decrease as more is learned about the asteroid. (The next opportunity for studying 1950 DA via radar is in 2032.)

There are many factors that influence the path of an asteroid through space. Its spin rate, reflectivity (albedo), composition, mass, terrain variations… gravitational interactions with other bodies, some of which may not even have been discovered yet… all of these can affect the movement of an asteroid and, more specifically, its exact position at a future point in time. While many of these things still aren’t precisely known for 1950 DA, one in particular could end up being the saving grace for our descendants: the Yarkovsky effect.

PHOTOS: Russian Meteor Strike Aftermath

A small but important force acting upon asteroids, the Yarkovsky effect is a “nudge” created by thermal emission. As an asteroid gathers heat energy from the sun, it releases some of that energy back into space. Thanks to Newtonian mechanics the sheer act of doing so creates a physical push back on the asteroid itself, altering its course ever so slightly. Over a long span of time, this slight alteration could result in the relocation of 1950 DA away from the spot in space where Earth will be on March 16, 2880… at least enough so that a miss is certain.

In fact, recent research by JPL scientists D. Farnocchia and S.R. Chesley have taken into consideration the Yarkovsky effect on 1950 DA based on known values from previous observations, as well as new research suggesting that the asteroid has a retrograde rotation. While their latest assessment does put the risk of an impact in 2880 within the lower end of the probability spectrum (4×10^-4, or -0.58 on the Palermo Scale) it is still far from zero, and in fact remains higher than any other known potential impacts.

PHOTOS: NASA’s Asteroid Capture Mission

So what would happen if the half-mile-wide 1950 DA were to hit Earth? While that depends on a lot of things, such as its composition, speed, angle of impact, where it impacts, etc., needless to say it would cause a lot of damage across a large area. I’m talking an energy release upwards of half a million megatons, which, were it to strike say, New York City, everything within at least a 100-mile radius would be flattened by the force of the impact alone — that’s halfway to Boston and Washington, DC. And that’s not even taking into consideration the air blast, atmospheric dust cloud, secondary impacts from debris, or damage from any resulting tsunami (if the impact were in the ocean)… the destruction would easily extend out many more hundreds of miles, and the repercussions — physical, financial, economic, and emotional — would extend around the globe.

But again, precisely where 1950 DA will be in another 866 1/2 years (and whether or not it will occupy the same point in space as our planet) relies on many factors that aren’t well known — even though its orbit is pretty well understood. More in-depth observations will need to be made, and that is why asteroids like this must be carefully — and continually — watched.

Luckily, 35 generations offers plenty of time to improve our knowledge. According to JPL’s Near-Earth Object program, “If it is eventually decided 1950 DA needs to be diverted, the hundreds of years of warning could allow a method as simple as dusting the surface of the asteroid with chalk or charcoal, or perhaps white glass beads, or sending a solar sail spacecraft that ends by collapsing its reflective sail around the asteroid. These things would change the asteroids reflectivity and allow sunlight to do the work of pushing the asteroid out of the way.”

ANALYSIS: Meet Asteroid 2013 MZ5, 10,000th Near-Earth Object

Still, whether because of ongoing research, faith in future generations of scientists, or just sheer probability, JPL remains confident that 1950 DA should cause little concern. “The most likely result will be that St. Patrick’s Day parades in 2880 will be a little more festive than usual as 1950 DA recedes into the distance, having passed Earth by.”

Let’s just hope the luck of the Irish is with our planet big time that year…

Source

January 9, 2013

Asteroid Apophis to whiz past Earth tonight — and return for more in 2036

An artist's rendering of the asteroid Apophis. (European Space Agency)

An artist’s rendering of the asteroid Apophis. (European Space Agency)

A European space telescope has captured new images of the huge asteroid Apophis, revealing that the potentially hazardous object is actually bigger than previously thought — and you have a chance to see the space rock yourself in two free webcasts tonight.

Asteroid Apophis has long been billed as a “doomsday asteroid” because of a 2004 study that predicted a 2.7 percent chance of the space rock hitting Earth when it passes within 22,364 miles of the planet in April 2029, European Space Agency officials said. Later studies proved, however, that the asteroid poses no threat to Earth during that flyby, but astronomers continue to track the object since it will make another pass near Earth in 2036.

 

Today, ESA officials announced that its infrared Herschel Space Observatory has discovered that Apophis is about 1,066 feet wide, nearly 20 percent larger than a previous estimate of 885 feet.

“The 20 percent increase in diameter … translates into a 75 percent increase in our estimates of the asteroid’s volume or mass,” study leader Thomas Müller of the Max Planck Institute for Extraterrestrial Physics in Garching, Germany, said in a statement. [Photos of Near-Earth Asteroid Apophis]

‘Alone among all these near-Earth asteroids that have passed our way in recent years, Apophis has generated the most concern worldwide.’

- Slooh president Patrick Paolucci

Tonight’s two free webcasts will stream live views of Apophis from telescopes in Italy and the Canary Islands tonight (Jan. 10). The webcasts, offered by the stargazing websites Slooh Space Telescope and Virtual Telescope Project, will show Apophis as a bright light moving across the night sky. The asteroid is too small to be seen through small backyard telescopes.

The Slooh Space Camera webcast will begin at 7 p.m. EST (0000 Jan. 10 GMT). The Virtual Telescope webcast will begin an hour later at 8 p.m. EST (0100 GMT). You can watch both live webcasts of asteroid Apophis here on SPACE.com tonight.

Apophis will be just under 9.3 million miles from Earth at the time of tonight’s webcasts, amateur astronomer Gianluca Masi of the Virtual Telescope Project told SPACE.com.

“Alone among all these near-Earth asteroids that have passed our way in recent years, Apophis has generated the most concern worldwide because of its extremely close approach in 2029 and [chances of a] potential impact, albeit small, in 2036,” Slooh president Patrick Paolucci said in a statement.

In addition to asteroid Apophis, astronomers regularly scan the night sky for asteroids  that may pose a potential impact threat to Earth. NASA’s Near-Earth Object Office and Asteroid Watch program is based at the agency’s Jet Propulsion Laboratory in Pasadena, Calif.

You can track Apophis directly via the Virtual Telescope Project here: http://www.virtualtelescope.eu/webtv/

The webcast from the Slooh Space Camera can also be seen here: http://events.slooh.com/
Source

July 11, 2012

New moon found orbiting demoted dwarf planet Pluto

Filed under: Cool, Kuiper Belt, Outer Solar System, Space Exploration — bferrari @ 3:49 pm
Photos of far-off Pluto taken by the Hubble telescope aren't sharp enough to see craters or mountains, if they exist on the surface, but Hubble reveals a complex-looking and variegated world with white, dark-orange, and charcoal-black terrain. (NASA, ESA, and M. Buie)

Photos of far-off Pluto taken by the Hubble telescope aren’t sharp enough to see craters or mountains, if they exist on the surface, but Hubble reveals a complex-looking and variegated world with white, dark-orange, and charcoal-black terrain. (NASA, ESA, and M. Buie)

A fifth moon has been discovered orbiting former planet Pluto, scientists with the Hubble Space Telescope announced Wednesday — but it’s still not enough to bump the dwarf planet back into the big leagues.

“Just announced: Pluto has some company — we’ve discovered a 5th moon using the Hubble Space Telescope!” Alan Stern, of the Southwest Research Institute in Boulder, Colo., announced via Twitter.

Stern is principal investigator of NASA’s New Horizons spacecraft, which is scheduled to fly by the Pluto system in 2015, according to Space.com. That will be the first mission ever to visit Pluto.

Just don’t call it a planet.

In 2006, the International Astronomical Union sent Pluto down to the minor leagues, labeling what had been the ninth planet orbiting our sun a “dwarf planet” instead. In spite of its many moons — including the new one, tentatively named P5 — Pluto has more in common with the other icy asteroids and planetoids orbiting with it in the “Kuiper Belt” beyond Neptune, the IAU said, than with Saturn, Uranus and Earth.

“[Pluto's] moons form a series of neatly nested orbits, a bit like Russian dolls,” said team lead Mark Showalter of the SETI Institute in Mountain View, Calif.

So five moons later, Pluto’s still not a planet — though it is a very complex system. Scientists believe the many moons are relics of a collision between Pluto and another large object billions of years ago.

P5 joins Charon, Nix, Hydra, and P4 in orbit around the dwarf. It’s estimated to be irregular in shape and 6 to 15 miles across. It is in a 58,000-mile-diameter circular orbit around.

“The discovery of so many small moons indirectly tells us that there must be lots of small particles lurking unseen in the Pluto system,” said Harold Weaver of the Johns Hopkins University Applied Physics Laboratory.
Or should they be called dwarf moons?

Read more: http://www.foxnews.com/scitech/2012/07/11/pluto-has-fifth-moon-hubble-telescope-reveals/?intcmp=features#ixzz20LiAssec

November 20, 2008

Signs of Weather Seen on Dwarf Planet

Filed under: Dwarf Planets, Kuiper Belt, Outer Solar System — bferrari @ 9:35 pm
This artist rendering shows the dwarf planet, Eris, with hte sun in the background. The discovery of Eris by Mike Brown of Caltech was announced on July 29, 2005. (NASA/JPL/Caltech)

This artist rendering shows the dwarf planet, Eris, with hte sun in the background. The discovery of Eris by Mike Brown of Caltech was announced on July 29, 2005. (NASA/JPL/Caltech)

Signs of Weather Seen on Dwarf Planet

By Jeanna Bryner
Senior Writer
posted: 18 November 2008
08:25 am ET

Strange weather on the icy dwarf planet Eris could be causing changes that scientists are now seeing at the methane-ice sufrace of this distant object in our outer solar system.

Eris is the largest known solar-system object beyond the orbit of Neptune. It is larger than Pluto, with a diameter of ranging somewhere between about 1,490 miles and 1,860 miles (2,400 km and 3,000 km).

A team of researchers examined data on Eris collected from the MMT Observatory in Arizona. They specifically looked at concentrations of methane ice based on light-reflection and absorption information.

Their results show possibly nitrogen ice mixed in with the methane ice covering Eris’ surface. And the relative amount of nitrogen ice increases with depth into the ice, they found.

Story continues after the jump: http://www.space.com/scienceandastronomy/081118-st-dwarf-planet.html

This illustration of the largest known Kuiper Belt Objects shows Xena slightly larger than Pluto. (NASA, ESA, and A. Feild (STScI))

This illustration of the largest known Kuiper Belt Objects shows Xena (later to be called Eris) slightly larger than Pluto. (NASA, ESA, and A. Feild (STScI))

Bob Ferrari writes:

Incidentally it was the discovery of this dwarf planet Eris that lead to the downgrading of Pluto from a planet down to a dwarf planet.

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