Starship Asterisk*

JohnD wrote:All,
A recent APOD, of the Almahata Sita meterorite led to all sorts of allegations here about the veracity of the report, as there was no crater.
See: http://apod.nasa.gov/apod/ap090328.html
and the thread here on this site.

Now Opportunity has encountered the "youngest crater seen on Mars". It may be only 100,000 years old!
See: http://marsrovers.jpl.nasa.gov/spotlight/20090429.html

A meteroid impact on Earth and Mars will be completely different, due to atmosphere and gravity.
But how big would have been the rock that caused Resolution crater?

And how about this as an Apod?
John

JohnD wrote:A meteroid impact on Earth and Mars will be completely different, due to atmosphere and gravity.
But how big would have been the rock that caused Resolution crater?

JohnD wrote:And why aren't Earth and Mars so different, Chris? The Almahata thread made the point that a meteorite as small as that would be slowed in Earth's atmosphere to a terminal velocity too small to cause a crater. Which wouldn't be true on Mars (?). Would a very much faster impact from as small an object cause such a crater?

http://www.planetary.org/blog/article/00002138/ wrote:
2008 TC3: One year later (a 365 Days of Astronomy podcast)
By Emily Lakdawalla Oct. 5, 2009 | 14:53 PDT | 21:53 UTC

<<Tomorrow it'll be one year exactly since the first time ever an astronomer on Earth discovered an object that had a 100% certainty of hitting the planet. Fortunately, the object named 8TA9D69, then renamed 2008 TC3, turned out to be small enough not to present any real hazard to anybody or anything on the ground. There was a special session at the Division of Planetary Sciences meeting on 2008 TC3 today (called "From the Heavens to the Earth: The 2008 TC3 / Almahata Sitta Ureilite Fall"), with presentations on the discovery and observations of 2008 TC3 in space, the discovery of meteorites on the ground, and detailed analysis of those meteorites. There was no Earth-shakingly new science in any of the abstracts or the associated press release. They did note that the asteroid is "among the most cooked of all known meteorites" yet it still contains "polycyclic aromatic hyrdrocarbons in high abundances" and "amazingly...some amino acids have survived."

I think the coolest thing released today were these two videos. The first represents actual telescopic images of 2008 TC3. The video is sped up of course, but even accounting for the fact that it's a time-lapse video I get a real sense of how incredibly speedily 2008 TC3 must have been moving across the sky from the incredible smear and rate of motion of the star trails. >>

This image of asteroid 2008 TC3 exploding in the atmosphere above northern Sudan
was taken by local resident Muawia Shaddad on the morning of October 7, 2008.

Scientists from all over the world are taking a second, more expansive, look at the car-sized asteroid that exploded over Sudan's Nubian Desert in 2008. Initial research was focused on classifying the meteorite fragments that were collected two to five months after they were strewn across the desert and tracked by NASA's Near Earth Object astronomical network. Now in a series of 20 papers for a special issue of the journal Meteoritics and Planetary Science, published on December 15, researchers have expanded their work to demonstrate the diversity of these fragments, with major implications for the meteorite's origin.

In the first round of research, Carnegie Geophysical scientist Doug Rumble, in collaboration with Muawia Shaddad of the University of Khartoum, examined one fragment of the asteroid, called 2008 TC3, and determined that it fell into a very rare category of meteorite called ureilites. Ureilites have a very different composition from most other meteorites. It has been suggested that all members of this meteoric family might have originated from the same source, called the ureilite parent body, which could have been a proto-planet.

Now Rumble has expanded his work to examine 11 meteorite fragments, focusing on the presence of oxygen isotopes. Isotopes are atoms of the same element that have extra neutrons in their nuclei.

Rumble explains: "Oxygen isotopes can be used to identify the meteorite's parent body and determine whether all the fragments indeed came from the same source. Each parent body of meteorites in the Solar System, including the Moon, Mars, and the large asteroid Vesta, has a distinctive signature of oxygen isotopes that can be recognized even when other factors, such as chemical composition and type of rock, are different."

Rumble and his team prepped tiny crumbs of these 11 meteorite fragments and loaded them into a reaction chamber where they were heated with a laser and underwent chemical reactions to release oxygen and then used another device, called a mass spectrometer, to measure the concentrations of these oxygen isotopes. Results showed that the full range of oxygen isotopes known to be present in ureilites were also present in the studied fragments.

"It was already known that the fragments in the Nubian Desert came from the same asteroid. Taking that into account, these new results demonstrate that the asteroid’s source, the ureilite parent body, also had a diversity of oxygen isotopes," says Rumble.

The diversity of oxygen isotopes found in ureilites probably arises from the circumstances of the parent this body's formation. Rumble theorizes that the rock components of this parent body were heated to the point of melting and then cooled into crystals so quickly that the oxygen isotopes present could not come to an equilibrium distribution throughout.

Together the collection of 20 papers published in Meteoritics and Planetary Science offer enormous insight about the formation and composition of ureilites and their hypothesized parent body.
__________________

For more information on the Seti Asima project visit: http://asima.seti.org/2008TC3/.

Researchers from the NASA Astrobiology Program have discovered amino acids in a meteorite where none were expected.

“This meteorite formed when two asteroids collided,” said Dr. Daniel Glavin of NASA’s Goddard Space Flight Center, Greenbelt, Md. “The shock of the collision heated it to more than 2,000 degrees Fahrenheit, hot enough that all complex organic molecules like amino acids should have been destroyed, but we found them anyway.” Glavin is lead author of a paper on this discovery appearing December 15 in Meteoritics and Planetary Science. “Finding them in this type of meteorite suggests that there is more than one way to make amino acids in space, which increases the chance for finding life elsewhere in the Universe.”

Amino acids are used to make proteins, the workhorse molecules of life, used in everything from structures like hair to enzymes, the catalysts that speed up or regulate chemical reactions. Just as the 26 letters of the alphabet are arranged in limitless combinations to make words, life uses 20 different amino acids in a huge variety of arrangements to build millions of different proteins. Previously, scientists at the Goddard Astrobiology Analytical Laboratory have found amino acids in samples of comet Wild 2 from NASA’s Stardust mission, and in various carbon-rich meteorites. Finding amino acids in these objects supports the theory that the origin of life got a boost from space — some of life’s ingredients formed in space and were delivered to Earth long ago by meteorite impacts.

When Dr. Peter Jenniskens of the SETI Institute, Mountain View, Calif., and NASA’s Ames Research Center, Moffett Field, Calif., approached NASA with the suggestion to search for amino acids in the carbon-rich remnants of asteroid 2008 TC3, expectations were that nothing was to be found. Because of an unusually violent collision in the past, this asteroid’s ingredients for life were a “culinary disaster” and now mostly in the form of graphite. The small asteroid, estimated at six to fifteen feet across, was the first to be detected in space prior to impact on Earth on October 7, 2008. When Jenniskens and Dr. Muawia Shaddad of the University of Khartoum recovered remnants in the Nubian Desert of northern Sudan, the remnants turned out to be the first Ureilite meteorites found in pristine condition.

A meteorite sample was divided between the Goddard lab and a lab at the Scripps Institution of Oceanography at the University of California, San Diego. “Our analyses confirm those obtained at Goddard,” said Professor Jeffrey Bada of Scripps, who led the analysis there. The extremely sensitive equipment in both labs detected small amounts of 19 different amino acids in the sample, ranging from 0.5 to 149 parts per billion. The team had to be sure that the amino acids in the meteorite didn’t come from contamination by life on Earth, and they were able to do so because of the way amino acids are made. Amino acid molecules can be built in two ways that are mirror images of each other, like your hands. Life on Earth uses left-handed amino acids, and they are never mixed with right-handed ones, but the amino acids found in the meteorite had equal amounts of the left and right-handed varieties.

The sample had various minerals that only form under high temperatures, indicating it was forged in a violent collision. It’s possible that the amino acids are simply leftovers from one of the original asteroids in the collision – an asteroid that had better conditions for amino acid formation. Dr. Jennifer Blank of SETI has done experiments with amino acids in water and ice, showing they survive pressures and temperatures comparable to a low-angle comet-Earth impact or asteroid-asteroid collisions.

However, the team thinks it’s unlikely amino acids could have survived the conditions that created the meteorite, which endured higher temperatures – more than 2,000 degrees Fahrenheit (over 1,100 Celsius) – over a much longer period. “It would be hard to transfer amino acids from an impactor to another body simply because of the high-energy conditions associated with the impact,” said Bada.

Instead, the team believes there’s an alternate method for making amino acids in space. “Previously, we thought the simplest way to make amino acids in an asteroid was at cooler temperatures in the presence of liquid water. This meteorite suggests there’s another way involving reactions in gases as a very hot asteroid cools down,” said Glavin. The team is planning experiments to test various gas-phase chemical reactions to see if they generate amino acids.

Fragments of 2008 TC3 are collectively called “Almahata Sitta” or “Station Six” after the train stop in northern Sudan near the location where pieces were recovered. They are prized because they are Ureilites, a rare type of meteorite. “An interesting possibility is that Ureilites are thought by some researchers to have formed in the solar nebula and thus the findings of amino acids in Almahata Sitta might imply that amino acids were in fact synthesized very early in the history of the solar system,” adds Bada.

An international team of scientists studying remnants of an asteroid that crashed into the Nubian Desert in October 2008 discovered it contained at least 10 different types of meteorites. Some of them contained chemicals that form the building blocks of life on Earth, and those chemicals were spread through all parts of the asteroid by collisions.

Chemists at Stanford University found that different meteorite types share the same distinct fingerprint of polycyclic aromatic hydrocarbons (PAHs). These complex organic molecules are distributed throughout the galaxy and form on Earth from incomplete combustion.

A research team from NASA's Goddard Space Flight Center in Greenbelt, Md., found amino acids in strongly heated fragments of the asteroid, where all such molecules should have been destroyed. Both PAHs and amino acids are considered building blocks of life.

Before landing on Earth, the 13-foot asteroid was detected by a telescope from the NASA-sponsored Catalina Sky Survey based at the University of Arizona in Tucson. Hours prior to its demise, astronomers and scientists around the world tracked and scanned the asteroid. It was the first time a celestial object was observed prior to entering Earth's atmosphere.

NASA's Jet Propulsion Laboratory in Pasadena, Calif., created a search grid and impact target area. The data helped Peter Jenniskens, an astronomer at NASA's Ames Research Center in Moffett Field, Calif., and the SETI Institute of Mountain View, Calif., guide a recovery team from the University of Khartoum in Sudan to search the desert landscape. During four expeditions, approximately 150 students recovered nearly 600 meteorite fragments weighing a total of more than 23 pounds.

"Right from the start, the students were surprised to find so much diversity in meteorite texture and hue," said Muawia Shaddad, an astronomer at the University of Khartoum, who led the search effort. "We estimate the asteroid initially weighed about 59 tons, of which about 86 pounds survived the explosion high in the atmosphere."

Subsequently, scientists determined most of the fragments are a rare type of meteorite called ureilites. Less than 10 of the nearly 1,000 known meteorites are ureilites. The recovery team made history when they found the first-ever freshly fallen mixed-composition, or polymict ureilite. The majority of the remaining fragments are similar to the more common types of meteorites called chondrites.

Other Ames researchers showed the ureilite fragments contained widely varying amounts of the minerals called olivine and pyroxene. Carnegie Institute of Washington researchers found these minerals have the full range of oxygen atom signatures detected in previous ureilites. Scientists believe this is evidence all ureilites originated from the same source, called the ureilite parent body. Astronomers theorize the parent body experienced a giant collision approximately 4.5 billion years ago and caused iron-rich minerals to smelt into metallic iron. However, the olivine and pyroxene didn't melt, which allowed the oxygen atoms in them to stay in the same arrangement as when they first formed.

Researchers at NASA's Johnson Space Center in Houston were able to deduce that much of the ureilite parent body was reduced to fragments measuring 30 to 300 feet during this giant collision. After the catastrophic collision, scientists believe the material that ended up making 2008 TC3 had a long history of violent collisions and impacts. These later collisions ground the fragments down into the smaller sand grain-sized pieces that gathered loosely together with many voids.

Researchers believe the amino acids were delivered to 2008 TC3 during the later impacts, or formed directly from trapped gases as the asteroid cooled following the giant collision. Other non-ureilite types of meteorites also became part of the asteroid. To date, ten different meteorite types have been identified, accounting for 20-30 percent of the asteroid's recovered remains.

"Asteroids have just become a lot more interesting," Jenniskens said. "We were surprised to find that not all of the meteorites we recovered were the same, even though we are certain they came from the same asteroid."

Astronomers have known asteroids orbiting the sun frequently are broken and reassembled during collisions, but until now they thought little mixing occurred because asteroids, or impactors that broke them apart, are usually very small. The research is featured in 20 papers published this week in an issue of the Meteoritical Society's journal Meteoritics and Planetary Science.

Click to view full size image

Scientists have discovered that an asteroid that crashed into the Nubian Desert in 2008 delivered at least 10 different types of meteorites. Some of the meteorites contain chemicals that are thought to have been important for the origin of life on Earth.

Movie showing the discovery images of 2008 TC. Images taken at around 06:30 UTC on Oct. 6, 2008. The asteroid was at 19th magnitude and moving at 2.5 degrees per day.

Credit: Richard Kowalski and Ed Beshore, Catalina Sky Survey

bystander wrote:NASA Discovers Asteroid Delivered Assortment of Meteorites

<<The recovery team made history when they found the first-ever freshly fallen mixed-composition, or polymict ureilite.
The majority of the remaining fragments are similar to the more common types of meteorites called chondrites.>>

http://en.wikipedia.org/wiki/Ureilite wrote:
<<Ureilite (a.k.a., olivine-pigeonite achondrite) is a rare type of stony meteorite that has a unique mineralogical composition very different from that of other stony meteorites. This dark grey or brownish meteorite type is named after the village Novy Urey, Mordovia Republic of Russia, where a meteorite of this type fell on 4 September 1886. Notable ureilites are the Novo Urei and the Goalpara, also named for the town in which it landed (Goalpara, Assam India). On 7 October 2008, tiny asteroid 2008 TC3 entered the Earth's atmosphere and exploded an estimated 37 kilometers (23 mi) above the Nubian Desert in Sudan. Fragments of this asteroid were recovered the following December and were found to be ureilite. Scientists have discovered amino acids, the building blocks of life in this meteorite 2008 TC3 where none were expected taking into account the high temperatures reached in the explosion about 1000 ºC. Compared to most other meteorites, ureilites tend to have a high percentage of carbon (average 3% by weight) in the form of graphite and nanodiamonds. The diamonds, which are rarely more than a few micrometres in diameter, are probably the result of high pressure shockwaves produced by collisions of the ureilite parent body with other asteroids. Ureilites can be divided into two subcategories: monomict and polymict. Monomict ureilites are coarse grained with olivine usually more abundant than pyroxene. Polymict ureilites are a mixture of clasts of dissimilar composition.>>

http://www.geokhi.ru/~meteorit/opis/novo-urei-e.html wrote:

460 g piece of NOVO-UREI Ureilite
Mordovia Fall, September 4, 1886

<<The Novy Urey meteorite is the type specimen of a new type of meteorites, ureilites. Erofeev and Lachinov, Russian scientists, first discovered diamonds of cosmic origin in the Novy Urey (Cyrillic: Новый Урей).

"In the morning several peasants plowed their field 3 km from a village. The day was gloomy, the whole northeastern sky was covered by clouds. Suddenly a light appeared all around. In several seconds a strong report was heard, like a cannon or explosion. Then came a second, louder noise. With a loud noise a fireball fell to Earth a few meters from the peasants. Frightened, they did not know what to do. They fell to the ground and could not move for a long time. They thought it was a strong thunderstorm, and that thunderbolts were falling from the sky. Finally, one of them, more brave, came to the place where the thunderbolt had fallen, and to his surprise found only a shallow hole. In the middle of the hole a black stone lay half-buried in the soil."

- P.I. Baryshnikov, the teacher, Kirensk City, 1886 г.