Asteroids & The Asteroid Belt

[Pete Younger]

So is it possible that the asteroid belt was once two large bodies that collided?

 

[Timble2]

Planetary ramble

So is it possible that the asteroid belt was once two large bodies that collided?

The general consensus these days seems to be its that it's stuff left over from the early days of the the solar system when were numerous numerous tiny planets accreted out of a cloud of gas and dust around the sun. These frequently collided and either shattering or adhered together to form larger planets. The largest of these formed the basis of the current planets, as their gravity increased they swept up most of the debris and smaller bodies in their orbits.

Before things finally settled down a planet around the size of Mars is thought to have collided with the proto-Earth. The material splashed off by the impact eventually clumped together to form the Moon.

The major planets pretty much swept up the asteroids from their orbits, you only have to look at the surface of the moon or Mars to see the hammering the worlds received.

Between between Mars and Jupiter no major planet formed and the remaining fragment of the early accretions and shattering collisions are today's asteroid belt - the asteroid belt is more builder's rubble, or a failed planet than the results of the collision between two major planets.

Of course not all of the primeval asteroids were swept up and or shepherded into the asteroid, belt some are in highly elliptical orbits crossing the orbits or the inner planets - it's thought one of these did for the dinosaurs. There would be a far heavier bombardment except for Jupiter having swept in a lot of the bodies that cross its orbit, and its shepherding of the asteroid belt.

Phobos and Diemos were probably bodies that crossed Mars's orbit and were captured, but avoided running straight into the planet.

BTW Earth has a captured asteroid Cruithne, which is sometimes referred to as a second moon, although it's not actually in a simple orbit, but in a complex gravitational dance that loops it round the Earth but avoids hitting us.

You can find a more coherent explanation at:
http://www.astro.queensu.ca/~wiegert/3753/3753.html

 

[Pete Younger]

Thanks for that Timble, a little knowledge is not such a dangerous thing.

 

[Mal_Adjusted]

Asteroid named after ‘Hitchhiker’ humorist

Greets

Asteroid named
after ‘Hitchhiker’ humorist
Late British sci-fi author
honored after cosmic campaign
Douglas Adams, was the author of "The Hitchhiker's Guide to the Galaxy," a cult science-fiction comedy. He died suddenly after a heart attack in 2001 at the age of 49.
By Alan Boyle
Science editor
MSNBC
Updated: 8:55 p.m. ET Jan. 25, 2005

The week he died, science-fiction humorist Douglas Adams was honored with an asteroid named after one of the characters from his classic "Hitchhiker's Guide to the Galaxy." Now, almost four years later, Adams has his own name in the heavens as well — thanks to a campaign in which MSNBC.com played a part.

advertisement
Asteroid Douglasadams was among the 71 newly named celestial objects announced Tuesday by the International Astronomical Union's Minor Planet Center in Cambridge, Mass. Other honorees range from Ball Aerospace and the city of Las Vegas to the sometimes-overlooked co-discoverer of the DNA double helix, Rosalind Franklin.

But Adams' asteroid should hold special appeal for fans of science fiction and pop culture: His "Hitchhiker" saga, which traces the adventures of a motley interplanetary crew after Earth is destroyed to make way for a hyperspace bypass, started out as a BBC radio comedy. Eventually, the tale inspired a five-novel "trilogy" as well as a TV series, and a long-simmering movie version is due for release in May.

Asteroid tributes
When Adams died of a heart attack in 2001, at the age of 49, tributes came in from around the world — but one of the biggest tributes was actually announced just days before his death: the naming of an asteroid after Arthur Dent, the Earthling at the center of the "Hitchhiker" story.

Through the years, about 12,000 asteroids have been given proper names by the IAU's Committee on Small Body Nomenclature — including fictional characters as well as mythological names (Ceres and Quaoar) and real-life personages (Lincoln and Elvis). The names are traditionally proposed by a particular asteroid's discoverer. For example, the "Arthurdent" asteroid was so named at the suggestion of the man who actually found it, German astronomer Felix Hormuth.

But there's a backlog of not-yet-named asteroids, and so the discoverers occasionally take requests. That's where MSNBC.com enters into the story of Asteroid Douglasadams.

What's in a name?
In August 2003, we reported on the naming of seven asteroids after Columbia's fallen astronauts, and solicited readers' suggestions for future asteroid names. One reader, Sean Ferris, put Adams' name forward — and we took it a step further by seeing if there was an asteroid particularly fitting for the honor.

One prospect stood out: an asteroid given the provisional designation 2001 DA42, discovered by the Lincoln Near Earth Asteroid Research project, or LINEAR. It's a relatively unremarkable space rock, orbiting 224 million miles (358 million kilometers) from the sun in the main asteroid belt, between Mars and Jupiter. But its name held triple significance.

Not only did it memorialize the year of Adams' death (2001) and his initials (DA), but it also referenced the number 42 — which is absurdly meaningful in the "Hitchhiker" saga as the "answer to the Ultimate Question." (The problem was, no one ever knew precisely what the Ultimate Question was.)

We proposed the name to Brian Marsden, the Minor Planet Center's director and the secretary for the naming committee — and Marsden was tickled by the idea. "This was sort of made for him, wasn't it?" he recalled Tuesday.

Long process

It took almost a year and a half for the proposal to make its way through the relevant committees at LINEAR and the IAU — but Marsden finally issued the citations for Douglasadams and the 70 other named asteroids on Tuesday in Minor Planet Circular 53469.

Looking back, Marsden said the asteroid-naming process isn't always as fun as you might think. "It ought to be," he said. "But at times it can be very frustrating."


Some names had to be rejected this time around because they took the form of unpronounceable acronyms, running afoul of the IAU's rules. Another rule is that asteroids shouldn't be named after controversial historical figures such as Stalin or Hitler. That sparked a debate over a proposal to name an asteroid (1998 OU7) after the Prussian military strategist Carl von Clausewitz, Marsden said.

In the end, Asteroid Clausewitz was victorious. "It was decided he wasn't in the same class as Hitler," Marsden said.

Among the other notables on Tuesday's list:


* Rosfranklin (1997 PE6): Chemist Rosalind Franklin's work was instrumental in identifying the molecular structure of DNA, but she died without receiving due credit for her contribution.

* Ballaero (1925 BA): Recognizes Ball Aerospace and Technology Corp., which has contributed to the development of the Hubble and Spitzer space telescopes, the Deep Impact probe and other spacecraft.

* NEAT (2001 SS272): Named after the Near Earth Asteroid Tracking program. Other asteroids honor the Rome Planetarium in Italy and Kharkiv National University in Kiev.

* Wollstonecraft (2004 DA): Honors 18th-century feminist Mary Wollstonecraft. Other asteroids recognize theologians Roger Bacon and Thomas Woolston, and the recently appointed U.S. poet laureate, Ted Kooser.

* Las Vegas (2001 LV6): A celestial tribute to the Nevada city in honor of its centennial this year. Among other places newly honored by asteroid names are Sewanee in Tennessee, Bora-Bora and the Lithuanian city of Kaunas.

http://www.msnbc.msn.com/id/6867061/

mal

 

[ramonmercado]

Asteroids Caused The Early Inner Solar System Cataclysm

Asteroids Caused The Early Inner Solar System Cataclysm

Image of the lunar highlands. The new study by Strom, Malhotra, Kring and their Japanese colleagues indicates this terrain was bombarded mostly by asteroids - not comets - that were flung into the inner solar system when the asteroid belt was destabilized by migrating giant planets. The Earth was similarly bombarded but geological activity has erased most evidence of that bombardment. Credit: NASA.
Tucson (SPX) Sep 16, 2005
University of Arizona and Japanese scientists are convinced that evidence at last settles decades-long arguments about what objects bombarded the early inner solar system in a cataclysm 3.9 billion years ago.
Ancient main belt asteroids identical in size to present-day asteroids in the Mars-Jupiter belt - not comets - hammered the inner rocky planets in a unique catastrophe that lasted for a blink of geologic time, anywhere from 20 million to 150 million years, they report in the Sept. 16 issue of Science.

However, the objects that have been battering our inner solar system after the so-called Late Heavy Bombardment ended are a distinctly different population, UA Professor Emeritus Robert Strom and colleagues report in the article, "The Origin of Planetary Impactors in the Inner Solar System."

After the Late Heavy Bombardment or Lunar Cataclysm period ended, mostly near-Earth asteroids (NEAs) have peppered the terrestrial region.

Strom has been studying the size and distribution of craters across solar system surfaces for the past 35 years. He has long suspected that two different projectile populations have been responsible for cratering inner solar system surfaces. But there's been too little data to prove it.

Until now.

Now asteroid surveys conducted by UA's Spacewatch, the Sloan Digital Sky Survey, Japan's Subaru telescope and the like have amassed fairly complete data on asteroids down to those with diameters of less than a kilometer. Suddenly it has become possible to compare the sizes of asteroids with the sizes of projectiles that blasted craters into surfaces from Mars inward to Mercury.

"When we derived the projectile sizes from the cratering record using scaling laws, the ancient and more recent projectile sizes matched the ancient and younger asteroid populations smack on," Strom said. "It's an astonishing fit."

"One thing this says is that the present-day size-distribution of asteroids in the asteroid belt was established at least as far back as 4 billion years ago," UA planetary scientist Renu Malhotra, a co-author of the Science paper, said.

"Another thing it says is that the mechanism that caused the Late Heavy Bombardment was a gravitational event that swept objects out of the asteroid belt regardless of size."

Malhotra discovered in previous research what this mechanism must have been. Near the end of their formation, Jupiter and the other outer gas giant planets swept up planetary debris farther out in the solar system, the Kuiper Belt region.

In clearing up dust and pieces leftover from outer solar system planet formation, Jupiter, especially, lost orbital energy and moved inward closer to the sun. That migration greatly enhanced Jupiter's gravitational influence on the asteroid belt, flinging asteroids irrespective of size toward the inner solar system.

Evidence that main belt asteroids pummeled the early inner solar system confirms a previously published cosmochemical analysis by UA planetary scientist David A. Kring and colleagues.

"The size distribution of impact craters in the ancient highlands of the moon and Mars is a completely independent test of the inner solar system cataclysm and confirms our cosmochemical evidence of an asteroid source," Kring, a co-author of the Science paper, said.

Kring was part of a team that earlier used an argon-argon dating technique in analyzing impact melt ages of lunar meteorites - rocks ejected at random from the moon's surface and that landed on Earth after a million or so years in space.

They found from the ages of the "clasts," or melted rock fragments, in the breccia meteorites that all of the moon was bombarded 3.9 billion years ago, a true global lunar cataclysm. The Apollo lunar sample analysis said that asteroids account for at least 80 percent of lunar impacts.

Comets have played a relatively minor role in inner solar system impacts, Strom, Malhotra and Kring also conclude from their work. Contrary to popular belief, probably no more than 10 percent of Earth's water has come from comets, Strom said.

After the Late Heavy Bombardment, terrestrial surfaces were so completely altered that no surface older than 3.9 billion years can be dated using the cratering record. Older rocks and minerals are found on the moon and Earth, but they are fragments of older surfaces that were broken up by impacts, the researchers said.

Strom said that if Earth had oceans between 4.4 billion and 4 billion years ago, as other geological evidence suggests, those oceans must have been vaporized by the asteroid impacts during the cataclysm.

Kring also has developed a hypothesis that suggests that the impact events during Late Heavy Bombardment generated vast subsurface hydrothermal systems that were critical to the early development of life. He estimated that the inner solar system cataclysm produced more than 20,000 craters between 10 kilometers to 1,000 kilometers in diameter on Earth.

Inner solar system cratering dynamics changed dramatically after the Late Heavy Bombardment. From then on, the impact cratering record reflects that most objects hitting inner solar system surfaces have been near-Earth asteroids, smaller asteroids from the main belt that are nudged into terrestrial-crossing orbits by a size-selective phenomenon called the Yarkovsky Effect.

The effect has to do with the way asteroids unevenly absorb and re-radiate the sun's energy. Over tens of millions of years, the effect is large enough to push asteroids smaller than 20 kilometers across into the jovian resonances, or gaps, that deliver them to terrestrial-crossing orbits.

The smaller the asteroid, the more it is influenced by the Yarkovsky Effect.

Planetary geologists have tried counting craters and their size distribution to get absolute ages for surfaces on the planets and moons.

"But until we knew the origin of the projectiles, there has been so much uncertainty that I thought it could lead to enormous error," Strom said. "And now I know I'm right. For example, people have based the geologic history of Mars on the heavy bombardment cratering record, and it's wrong because they're using only one cratering curve, not two."

Attempts to date outer solar system bodies using the inner solar system cratering record is completely wrong, Strom said. But it should be possible to more accurately date inner solar system surfaces once researchers determine the cratering rate from the near-Earth asteroid bombardment, he added.

The authors of the Science paper are Strom, Malhotra and Kring from the University of Arizona Lunar and Planetary Laboratory, and Takashi Ito and Fumi Yoshida of National Astronomical Observatory, Tokyo, Japan.

http://www.spacedaily.com/news/asteroid-05q.html

 

[Rubyait]

New data reveals mysteries of asteroid Itokawa

Close-up views of asteroid Itokawa taken by Japan's Hayabusa spacecraft at the end of 2005 continue to puzzle scientists. They debated nearly every aspect of the asteroid – including its formation, age and composition – during the first major release of mission data on Friday.

Hayabusa was designed to bring the first asteroid samples back to Earth by firing pellets into the space rock and scooping up the resulting debris. But it probably failed to fire any pellets during two landings on Itokawa in November 2005, making it unlikely to have captured much – if any – rocky debris.

However, the spacecraft took high-resolution images, spectra and density measurements of the 550-metre-long space rock, and mission scientists presented the observations at the Lunar and Planetary Science Conference in Houston, Texas, US.

"We'd learn a lot more if we got samples back," says Jay Melosh, a planetary scientist at the University of Arizona in Tucson, US, who was not involved with the mission. "But it's given us a glimpse of a kind of object we've never seen before."

Shaken up
Most asteroids appear to be covered largely by fine regolith – the rock dust created by the impact of small meteorites. But Itokawa contains only small amounts – its finest-grain material appears to be gravel-sized particles. "This suggests there is some process removing fine dust or burying it under the surface," Melosh told New Scientist.

Furthermore, the gravel-like regolith is not distributed evenly but is concentrated in flat expanses that cover about one-fifth of Itokawa's surface. The rest of the surface is "rough" terrain littered with metre-sized boulders, which suggests that some process is moving the gravel into the flat zones.

One possible mechanism could be impacts by other space rocks. Melosh and his colleagues have previously shown that impacts on small asteroids could cause them to shake for several hours, moving regolith around their surfaces.

Age range
This shaking might also explain another of Itokawa's mysteries, says Hayabusa team member Naru Hirata of Kobe University in Japan, by covering up craters. Researchers see far fewer craters than they expect – just 60 candidates larger than a few metres across. Alternatively, he says, small craters may never form in the first place – a small meteoroid hitting Itokawa may simply crush one of the many boulders on its surface and not produce a crater.

Such effects imply Itokawa has been pummelled by more space rocks than its youthful appearance suggests. Assuming that this is the case, Chikatoshi Honda of the Japan Aerospace Exploration Agency (JAXA) in Kanagawa, Japan, estimates it is between 10 million and 100 million years old.

But other team members argue that the dearth of craters should be taken at face value – and that Itokawa is genuinely young. Itokawa is thought to have formed just outside the orbit of Mars in the main asteroid belt between Mars and Jupiter. Then, close encounters with Mars probably pulled it closer to the Sun into its current orbit, which crosses that of the Earth, says team member Makoto Yoshikawa of JAXA.

Rubble fusion
But its current orbit is very sensitive to the gravity of objects around it, making long-term estimates of its past or future motion difficult. Given this uncertainty, Itokawa "could have formed only one or two million years ago", says team member Andy Cheng of Johns Hopkins University in Maryland, US.

He says the asteroid may have quickly left the asteroid belt, where it would have had the highest chance of being struck by other space rocks, and spent most of its lifetime within the orbit of Mars.

Researchers are also divided over how Itokawa formed. Estimates of its density reveal it is 39% empty space. That suggests it coalesced from the debris of an ancient asteroid impact. But whether it formed as a single rubble pile or as two that later collided and stuck together remains unclear.

Hayabusa team members favour the latter scenario, pointing out that its shape resembles a sea otter, with a small head curving towards a larger body. They say these two components were once separate and at some point fused together at the "neck".

Hot and cold
But Melosh says typical collisions in the asteroid belt occur at speeds of 2 kilometres per second – too fast for objects to attach to one another. If Itokawa is a so-called "contact binary", he says, the collision would have to have been "a very special event at very, very low velocity". Instead, he says Itokawa may have been stretched into an elongated shape by an external gravity field as it passed by a massive object, such as the Earth.

The rock's composition is also unclear. Spectral observations of minerals taken from Hayabusa suggest the rock was not altered by heat in its past. But those from ground-based telescopes in Hawaii suggest it partially melted after being heated to more than 1000°C.

Pinning this history down may reveal when and where in the solar system its component rocks formed. And that would inform how to interpret the histories of meteorites that fall to Earth.

Ion engines
But the issue can only be settled definitively by studying samples returned from the asteroid, says Melosh. Mission members hope the spacecraft accidentally collected some dust from the asteroid during its two landings and are hoping to send the probe back towards Earth in early 2007.

But it is far from certain that the spacecraft can make the journey. In December, the spacecraft spun out of control after a fuel leak and was out of contact with mission managers for more than a month, with its antenna pointing in the wrong direction. During this time, its circuits may have been damaged by the cold of space, mission manager Jun'ichiro Kawaguchi told New Scientist.

Now, mission managers are turning on all of the 200 or so heaters on the spacecraft and will test the first of the spacecraft's three ion engines in about a month, with the other two engines turned on successively over the next six months. The ion engines will be used to propel the craft back to Earth, so it is crucial that they function, says Kawaguchi. "As of today, we have not been able to confirm if the ion engines operate," he says.

http://www.newscientistspace.com/articl ... kawa-.html

 

[rynner2]

Record spin for newfound asteroid

The fastest spinning natural object in the Solar System has been discovered by a British amateur astronomer.

The compact stony asteroid 2008 HJ - completes a full rotation once every 42.7 seconds, according to its discoverer Richard Miles.

That measurement smashes the previous record held by the asteroid 2000 DO8, which spins once every 78 seconds.

The new finding was made by the amateur astronomer while operating the Faulkes Telescope South in Australia.

2008 HJ is estimated to be some 12m by 24m in size - smaller than a tennis court. Yet it probably has a mass in excess of 5,000 tonnes.

It was moving at almost 162,000km/h (100,000 mph) when it hurtled past the Earth in late April. Despite being classified as a "near-Earth asteroid", it came no closer than one million km and never posed a threat to our planet.

But the discovery adds to astronomers' sparse understanding of very small asteroids in near-Earth orbits.

Dr Petr Pravec, an astronomer at the Ondrejov Observatory in the Czech Republic, and an expert in the field, commented: "A period of 42.7 seconds for an asteroid with a size of about 20 meters is perfectly consistent with theory.

"There may be a significant population of asteroids measuring up to a few tens of metres across, rotating in less than a minute, that have not been observed until now."

Mr Miles made the discovery while operating the Australian telescope remotely, via the internet, from his home in Dorset.

http://news.bbc.co.uk/1/hi/sci/tech/7426755.stm

 

[eburacum]

The smaller an asteroid is, the faster it rotates (as a general rule). Asteroids smaller than 100 metres can spin so fast that gravity is negative along its equator, assuming a simple rotation. Since many ot these objects tumble, that is, rotate around more than one axis, you run the risk of being flung off at any time.

This makes mining or moving small tumbling asteroids difficult. As far as moving tumbling asteroids, here's a scheme we use in Orion's Arm;
http://www.orionsarm.com/ships/Gravity_Tug.html

 

[Xanatic_]

Asteroid explosion over Indonesia raises fears about Earth's defences

On 8 October, the rock crashed into the atmosphere above South Sulawesi, Indonesia. The blast was heard by monitoring stations 10,000 miles away, according to a report by scientists at the University of Western Ontario.

Scientists are concerned that it was not spotted by any telescopes, and that had it been larger it could have caused a disaster.

The asteroid, estimated to have been around 10 metres (30ft) across, hit the atmosphere at an estimated 45,000mph. The sudden deceleration caused it to heat up rapidly and explode with the force of 50,000 tons of TNT.

Luckily, due to the height of the explosion – estimated at between 15 and 20 km (nine to 12 miles) above sea level – no damage was caused on the ground.

However, if the object had been slightly larger – 20 to 30 metres (60 to 90ft) across – it could easily have caused extensive damage and loss of life, say researchers.

Very few objects smaller than 100 meters (300ft) across have been spotted and catalogued by astronomers.

Tim Spahr, director of the Minor Planet Center in Cambridge, Massachusetts, warned that it was inevitable that minor asteroids would go unnoticed. He said: "If you want to find the smallest objects you have to build more, larger telescopes.

"A survey that finds all of the 20-metre objects will cost probably multiple billions of dollars."

The fireball was spotted by locals in Indonesia, and a YouTube video taken that day "appears to show a large dust cloud consistent with a bright, daylight fireball", according to the Ontario researchers.

An asteroid or comet fragment around 60 meters across is believed to have been behind the Tunguska Event, a powerful explosion that took place over Russia in 1908. The blast has been estimated at equivalent to 10-15 million tons of TNT – enough to destroy a large city.

The White House is to develop a policy on the space object impact threat by October next year.

From http://www.telegraph.co.uk/science/...nesia-raises-fears-about-Earths-defences.html

I wondering about the part that says "hit the atmosphere at an estimated 45,000mph. The sudden deceleration caused it to heat up rapidly and explode with the force of 50,000 tons of TNT." Don´t astronomers usually say that meteors go too fast through the atmosphere to heat up to any meaningful temperature? Presumably this one would have needed to have gone from -273 to 600 degrees in the few seconds it moved through the atmosphere to explode.

 

[rynner2]

Nasa scientists use Hubble space telescope to capture head on asteroid collision
Nasa scientists using the Hubble space telescope have captured for the first time a close up view of a remarkable head-on collision between two asteroids, which could have been part of what killed off dinosaurs millions of years ago.
By Andrew Hough
Published: 7:30AM GMT 04 Feb 2010

The giant space rocks created a spectacular trail of debris as they collided at 11,000mph - five times the speed of a rifle bullet - between the orbits of Mars and Jupiter.

The cosmic pile-up is the first ever witnessed in the asteroid belt, 90 million miles away in space.

A fragment from the same family of asteroids is thought to have wiped out the dinosaurs 65 million years ago.

Scientists believe the find could help experts prevent any asteroid from colliding with the earth.

The fuzzy cloud from the debris was first photographed last month with a robotic camera called LINEAR that searches for asteroids in New Mexico.

It was so rare that Hubble was switched from its observing routine to get a close-up of it on January 29.

Lead scientist David Jewitt, from the University of California at Los Angeles, said: "The truth is we're still struggling to understand what this means. It's most likely the result of a recent collision between two asteroids.

"It would be the first case we've seen of an asteroid smash happening. It might help us understand how to destroy an asteroid and even prevent one from hitting us."

The picture, taken with upgraded Hubble's powerful new camera, shows a mysterious X-shaped pattern with trailing streamers of dust that suggest the collision was head-on, say experts.

The heart of the main rock, labelled P/2010 A2, can be seen as a bright star-like point outide its own halo of dust. This nucleus is estimated to be about 460 ft wide.

NASA says a study of the orbit of P/2010 A2 suggests it belongs to the Flora asteroid family - rocks which shattered into pieces in a bigger collision more than 100 million years ago.

But until now, no such asteroid-asteroid collision has been caught "in the act".

One fragment of that ancient smash is thought to have struck Earth 65 million years ago, triggering a mass extinction that wiped out the dinosaurs.

http://www.telegraph.co.uk/science/spac ... ision.html

 

[rynner2]

Bigger pic here
http://www.dailymail.co.uk/sciencetech/ ... ision.html

gives the context of the pic shown in the Telegraph, which only shows the head of a long chain of debris.

 

[rynner2]

Asteroid Themis has 'frosted surface'
Page last updated at 17:04 GMT, Wednesday, 28 April 2010 18:04 UK
By Jonathan Amos Science correspondent, BBC News

Scientists have detected water-ice on the surface of an asteroid.

The first-time observation was made on 24 Themis, a huge rock that orbits almost 480 million km out from the Sun.

The researchers say that ice is not stable in such circumstances and has to be being replenished by some means - perhaps from inside the object.

They tell Nature magazine the finding plays into the theory that much of the water in Earth's oceans was delivered from space.

"It's interesting that we have detected ice on an asteroid because there have been suggestions that water on Earth came from impacts with many asteroids in Earth's early history," said Professor Humberto Campins, from the University of Central Florida, Orlando, US.

"This detection of water-ice on the surface of an asteroid supports that idea," he told BBC News.

24 Themis is about 200km is diameter, making it one of the biggest rocks in the main asteroid belt. It orbits at more than one-and-a-half-times the Sun-Mars distance.

The observation that its surface is frosted was confirmed by two independent teams - one led by Professor Campins - who examined how light was reflected off the body using the US space agency's (Nasa) Infrared Telescope Facility on Mauna Kea, Hawaii.

The teams also found a signature for complex organic, or carbon-rich, compounds.

Scientists have long since detected hydrated, or water-containing, minerals on the surfaces of asteroids - but this is a first in terms of an observation of exposed water-ice.

The researchers were drawn to make the study because smaller fragments of the rock broken off during an ancient collision look rather like comets when viewed through telescopes, and this suggested they and the larger body might harbour significant quantities of ice.

But to find it covering the surface is unexpected, say the researchers. In sunlight, and with no pressure from an atmosphere, the ice would be expected to vaporise rapidly.

This indicates the ice disappearing at the surface is constantly being replaced.

One scenario thought highly unlikely is that Themis has had a recent collision with an icy comet.

More probable explanations are that frequent impacts with smaller rocks are turning over the surface to release hidden reserves of ice, or that vapour from ice held deeper inside the asteroid is continually out-gassing and condensing briefly on the surface.

Theorists have been concerned for some time that the Earth may have formed at too high a temperature to have started with much water, and it has become a popular theory that much of the water we see today must have come in from elsewhere.

Comets contain a lot of water and impacts could have delivered large volumes. But perhaps not enough, says Dr Andy Rivkin, from Johns Hopkins University, Laurel, US, who led the other research team.

Also, the type of atoms (isotopes) seen in Earth water do not match well a comet-only source.

"Finding ice in Themis and the Themis family opens up the possibility that you might have brought in water from asteroids as well as comets; and that potentially allows a lot more water to be brought in and it also allows the isotopic compositions to work out the way we need them to, to match the Earth," Dr Rivkin told BBC News.

Asteroids are a very fashionable topic for scientific study at the moment.

A Japanese capsule is due to return to Earth in a few weeks with a sample picked up off the surface of a space rock; the European Space Agency's Rosetta probe will flyby an asteroid later this year; and a Nasa spacecraft will go into orbit around one of these bodies in 2011.

President Barack Obama has also directed the US space agency to send astronauts to an asteroid in the mid-2020s.

"For a while we thought we knew everything there was worth knowing about asteroids, and we looked farther and farther out into the Solar System, to the moons of Jupiter and Saturn and to the Kuiper Belt," observed Dr Henry Hsieh from Queen's University Belfast, UK.

"Now there seems to be a lot going in the asteroid belt that we don't actually understand, so again these bodies are exciting."

http://news.bbc.co.uk/1/hi/science_and_ ... 090128.stm

 

[rynner2]

First pictures of largest asteroid Lutetia

[video]

http://news.bbc.co.uk/1/hi/science_and_ ... 588997.stm

It looks quite skull-like from some angles - the 'Face on Mars' gang will love it! 8)

 

[rynner2]

Our terrifyingly crowded solar system: How the asteroids are closing in
By Sophie Freeman and Carol Driver
Last updated at 9:45 AM on 27th August 2010

It's not just our country that's getting a little over-crowded - our whole solar system is too.

Fascinating colour-coded footage recorded over 30 years has documented the increasing number of asteroids flying close to Earth.
Created by British astronomer Scott Manley, the three-minute clip - which is the equivalent of two months per second - starts with a sprinkling of white 'dust' around the edge of the planets.

Over the years, and as more telescopes are added to the experiment, this becomes a dense green 'ring' as the number of 'minor planets' found in the asteroid belt increases.

Worryingly, the red dots are those which fly around the inside the Earth's orbit - with the footage showing that some appear dangerously close.
The final colour of an asteroid on the video indicates how closely it comes to the inner solar system - with yellow indicating Earth-approachers.

Mr Manley created 'maps' every day from 1980 to 2010 to pinpoint the location of asteroids discovered by telescopes.

Thirty years ago, there were just 8,954 within our solar system. Today, there are 530,091 - forming a green 'eye' of minor planets.

Mr Manley, a former research student at Armagh Observatory in Northern Ireland, said: 'The images are created by using the known orbits of the asteroids to figure out where they've been on a day-to-day basis.
'Just like we can figure out where the Earth, Mars and Venus have been, we can do the same with anything orbiting the sun.
'I created maps for every day over the last 30 years - that's about 11,000 images - then I combined them to make a video.'

Asteroids are small solar system bodies that orbit the sun. They are smaller than planets, and are sometimes referred to as minor planets.
Their size ranges from 950km for the largest known asteroid, Ceres, to just tens of metres across.

Small asteroids - five to 10 metres in diameter - enter the Earth's atmosphere about once a year, but normally explode before impact. Larger minor planets - of about 1km in size - strike every 500,000 years.

But although some of the asteroids on Mr Manley's map look as though they are terrifyingly close to the Earth, he has some words of reassurance.
'The positions are all to scale, but the sizes of objects are expanded to make them visible,' he said.
'One pixel on the screen is one million kilometres - so even if an asteroid appears right on top of Earth in the video it could be up to a million kilometres away. That's more than twice the distance to the Moon.'

Video: Best viewed in full screen...

Read more: http://www.dailymail.co.uk/sciencetech/ ... z0xnPZQ2NX

This article might give the impression the number of astroids is increasing, but they're not. They've always been there, but we were in blissful ignorance in earlier times. Since we've become aware of the danger of asteroid impact, we've been more actively looking for them, using improved technology, so we now know about many more.

I've seen similar videos of asteroid movement, but not covering a 30 year period like this one.

 

[Zilch5]

Two asteroids making a close approach

Within the space of less than an hour on September 5, the Mount Lemmon
Survey discovered two objects which will both pass by the Earth on September
8 at a distance closer than the Moon! This unprecedented coincidence
provides an exciting observing challenge for amateurs although those
observing from the UK will not have the best views.

The intrinsically smaller object, 2010 RF12, will be the more favourable
observing target in that it passes closest at about 0.21 lunar-distance,
i.e. about 80,000 km. Tonight from the UK (Sep 6/7) this object will be
17th magnitude but by tomorrow (Sep 7/8 ) it will be brightening rapidly from
16th to 15th magnitude and be accelerating from an apparent speed of about
30 "/min to 50 "/min. It passes closest around 2100 UT on the 8th but by
then it will be difficult from any location on the Earth.

The larger object, 2010 RX30, only approaches to within about 0.66
lunar-distances of the Earth but will be more favourably placed for UK
observers and should be able to be followed to within about 6 hours of
closest approach which takes place around 1000 UT on the 8th. It will be
visible all night on Sep 7/8 being 16th magnitude at first but then
brightening to 15th mag. The problem however is its apparent speed in that it will be racing across the sky at between 2-5 ARCSEC/SEC.

http://britastro.org/baa/index.php?opti ... mid=100009

 

[Cultjunky]

This sounds really interesting Zilch, but picture the Duck on your left in a blond wig. Now hold that thought. Add to the image insomnia, a couple of glasses of red, and nicotine deprivation. That's me that is. A Dumb Duck without a telescope, or a clue if I might be able to see anything. Heyalp Heyalp!

Seriously, will this be seen by the naked eye similar to a shooting star? Or will I have to hope for the Beeb to put up some shots the following day?

 

[Zilch5]

I think you might need a telescope - I'm not sure, but I don't have one either if that is of any consolation.

 

[rynner2]

Definitely NOT naked eye objects. The faintest objects most people can see in good condtions are around magnitude 6, and both these asteroids are much fainter than that, at around 15 at best.

Their speed, although very noticeable in a telescope, will be nothing like that of a shooting star (which is much closer to Earth, actually in our atmosphere).

And don't hold your breath for TV pictures - they'll probably just show (if shown at all) a point of light moving across the background of fixed stars! If a really big telescope could spare the time from its regular work, we might get a little more detail, but not as good as pictures of other asteroids taken from fly-by space probes. And a blurry pic of a space rock would not advance the cause of science much, but more precise details of its orbit would be useful.

 

[Cultjunky]

Thanks Guys

Oh well, never mind :?

 

[rynner2]

Today's Traffic: There are three objects known to be moving within ten lunar distances (LD) of our planet today, September 8th. 2010 RB12 departs from within ten LD today while two intruders are inside the Earth-Moon system.

2010 RF12 is coming its closest to Earth on this passage, reaching 0.21 LD at 2112 UTC.

2010 RX30 is moving from 1.12 to 1.46 LD, coming its closest to the Earth at 0.64 LD at 0950 UTC, and also its closest to the Moon at 0.89 LD at 1952 UTC.

No other objects are known to be coming in for a close approach to Earth until late this month.

There are five objects that recently flew past Earth at less than ten LD and remain of continuing active interest. See their details below.

This report was refreshed at 0206 UTC. New data has been posted today for one object: 2010 RL43 (new to this page).

http://www.hohmanntransfer.com/

Rather garish colours on that web page!

 

[rynner2]

Two large asteroids narrowly miss earth, Nasa said
Two large asteroids have narrowly avoided the earth after the objects passed within the moon and our planet’s orbit, Nasa scientists said.
By Andrew Hough, and Sarah Kelley
Published: 8:50AM BST 09 Sep 2010

The two objects were only identified at the weekend by the Nasa-funded Catalina Sky Survey near Tucson, Arizona, during a routine sky scan.

The first asteroid, christened 2010 RX30, was about 65 feet (20 metres) in diameter and flew past at a distance of 154,000 miles early at 09:51am on Wednesday.

The second, called 2010 RF12, was roughly two-thirds the size of its big brother and estimated to pass within just 49,088 miles of Earth hours later.
[In other words, they were very small asteroids. ]

While they were visible to many amateur stargazers, space agency researchers said neither asteroid posed a risk to earth.

Experts, however, said the “double-whammy” served as a reminder of other potentially hazardous objects expected to narrowly miss Earth in coming years.

Nasa estimates that asteroids smaller than 25 meters in diameter would burn up while entering the atmosphere and cause no damage.

Scientists said while it was common to witness a single asteroid at such close range it was rare to see [Garbled bollocks ] known to make such close passes but usually slip by unnoticed.

Figures show about 50 million NEO’s (Near Earth Objects) pass by every day.

But what made this event so significant was that the two asteroids passed so close to Earth on the same day within hours of each other.

"This is the first time we've seen (two) combined within a 24-hour period but that's probably because we don't know everything that is out there," said Lindley Johnson, program executive of the Near-Earth Object program at Nasa’s headquarters in Washington.

Donald Yeomans, another manager of the programme, which detects and tracks potentially hazardous asteroids and comets, said neither asteroid was visible to the naked eye.

He added that when they were nearest both asteroids were visible from moderate strength amateur telescopes.

In July, Nasa experts gave details of an asteroid measuring more than 600 yards wide, which has a one-in-a-thousand chance of colliding with Earth in 2182.

That collision promises to create more damage than that of the atomic bombing of Hiroshima.

Preceding this, Apophis, a 25 million ton celestial body will narrowly miss our planet three times in succession.

The first near-miss is expected on the superstitious date of Friday 13th 2029.

"I think this is Mother Nature's way of firing a shot over the bow and warning Earth-based astronomers that we have a lot of work to do." Dr Yeomans added.

http://www.telegraph.co.uk/science/spac ... roids.html

 

[rynner2]

Earth and Moon 'bombarded with large asteroids 3.9bn years ago'
Any life which may have existed on Earth 3.9 billion years ago would have been wiped out in a devastating asteroid strike, new analysis of Moon craters indicates.
By Matthew Moore
Published: 6:23PM BST 17 Sep 2010

Earth and its satellite were bombarded with large asteroids during the solar system’s “turbulent youth”, striking new topographical maps show.

The impacts would have been powerful enough to evaporate any water on our planet and destroy any early organisms.

The scale of the onslaught has been revealed by the most detailed analysis of Moon craters ever carried out by scientists.

A team led by researchers at Brown University in the US used a laser altimeter on board Nasa's Lunar Reconnaissance Orbiter to identify and map a total of 5,185 asteroid craters on the Moon’s surface. All of the craters are at least 20km in diameter.

They found that the largest craters tend to be clustered in regions where the surface of the Moon is older.

In areas where the surface is newer – having been formed by subsequent lava flows – the researchers found the average crater size is significantly smaller.

The evidence supports the view that the Moon and the Earth endured a bombardment of large asteroids around 3.9 billion years ago.

This is thought to have come to a halt a few hundred of millions of years later, when Jupiter and Saturn settled into their orbits and began to exert a different gravitational pull on the asteroid belt from where the missiles originated.

Since then, we have generally escaped the largest asteroids hurtling through space.

James W Head III, who led the research published in the journal Science, said that the findings "are telling us something about the infancy of the solar system."

He added: "It is clear we can find out and learn so much more from future missions, robotic or otherwise. There is so much to do."

Scientists are forced to analyse the Moon for clues our planet’s geological history because erosion has destroyed evidence of distant asteroid strikes on Earth.

Earth was formed around 4.5 billion years ago. Scientists are uncertain when life first emerged, but evidence indicates that microorganisms existed around 3.5 billion years ago.

http://www.telegraph.co.uk/science/spac ... s-ago.html

 

[eburacum]

This is the Late Heavy Bombardment, and previous to this study it was thought that life may have survived through it (major asteroid hits would be hundreds of years apart, allowing some period of recovery).

The LHB may have been caused by Neptune. According to a simulation from the University of Nice, Neptune used to be inside the orbit of Uranus. Because of a resonance between Jupiter and Saturn, Neptune was flung outwards into the Kuiper Belt, flinging asteroids into the inner system and elsewhere. This would have been traumatic, and possibly terminal, for any life on Earth (or on Venus or Mars).

But I still think life may have survived, if it existed. Some isotopic evidence dating back to before the LHB suggests that it may have.

 

[rynner2]

Early results from Rosetta's flyby of Lutetia:

Asteroid Lutetia has thick blanket of debris
By Jonathan Amos, Science correspondent, BBC News

About 100km wide, Lutetia is the biggest asteroid yet visited by a spacecraft Lutetia, the giant asteroid visited by Europe's Rosetta probe in July, is covered in a thick blanket of dusty debris at least 600m (2,000ft) deep.

Aeons of impacts have pulverised the space rock to produce a shattered surface that in terms of texture is much like Earth's Moon, scientists say.

The finding is one of the first to emerge from the wealth of data gathered by Rosetta during its close flyby.

etc...

http://www.bbc.co.uk/news/science-environment-11470851

At closest approach during the flyby, the resolution in Rosetta's pictures was about 60m per pixel, more than sufficient to pick out remarkable details on its surface.

But not necessarily good enough to pick up any Black Obelisks!

 

[rynner2]

Asteroid collision makes quite a picture

The dusty wreckage thrown out in the explosive collision of two asteroids has been pictured by spacecraft.

The debris stretches for hundreds of thousands of kilometres.

US and European scientists tell the journal Nature that a remnant rock about 120m in size sits at the head of this shattered stream of material.

Their investigations using the powerful imaging equipment on the Hubble telescope and the Rosetta probe suggest the pile-up occurred in early 2009.

Colin Snodgrass from the Max Planck Institute for Solar System Research, Katlenburg-Lindau, Germany, worked on the Rosetta data.

He said the event offered a unique observing opportunity for researchers studying the Solar System.

"If you look at the literature on 'recent' asteroid collisions, they talk about things occurring in the past million years - that's recent on geological timescales. But on the timescales involved in this event, we're really catching it in the moment of happening," he told BBC News.

http://www.bbc.co.uk/news/science-environment-11534216

 

[rynner2]

Dawn probe set to orbit Asteroid Vesta
By Jonathan Amos, Science correspondent, BBC News

The US space agency says its Dawn probe should go into orbit around the Asteroid Vesta early on Saturday (GMT).
The robotic satellite will be spending a year at the 530km-wide body before moving on to the "dwarf planet" Ceres.

New pictures on Dawn's approach to Vesta show the giant rock in unprecedented detail.
The asteroid looks like a punctured football, the result of a colossal collision sometime in its past that knocked off its south polar region.

Dawn's encounter is occurring about 188 million km (117 million miles) from Earth. Engineers have put the spacecraft on a course to be captured in the gravitational field of Vesta.
They expect to hear confirmation from the satellite on Saturday that it is safely circling the rock.
Initially, Dawn will be about 16,000km (9,900 miles) from the asteroid, but this distance will be reduced over time.

"It has taken nearly four years to get to this point," said Robert Mase, Dawn project manager at Nasa's Jet Propulsion Laboratory in Pasadena, California. "Our latest tests and check-outs show that Dawn is right on target and performing normally."

Scientists believe asteroids can help them understand more about the earliest days of the Solar System. These wandering rocks are often described as the rubble that was left over after the planets proper had formed.

Vesta and Ceres should make for interesting subjects. They are both evolved bodies - objects that have heated up and started to separate into distinct layers.
In the case of Vesta this probably means it has an iron core.

Ceres, which, at 950km in diameter, is by far the largest and most massive body in the asteroid belt, may not have got that far.
Scientists think it probably retains a lot of water, perhaps in a band of ice deep below the surface.

http://www.bbc.co.uk/news/science-environment-14160135

 

[OneWingedBird]

Perhaps it will get Marooned off Vesta :lol:

That was a brilliant story.

 

[Pete Younger]

Perhaps it will get Marooned off Vesta :lol:

That was a brilliant story.

Indeed, that was the launchpad for Asimov's career as a top notch SF writter.

 

[rynner2]

Dawn probe orbits asteroid Vesta
By Jonathan Amos, Science correspondent, BBC News

The Dawn probe has successfully entered orbit around the asteroid Vesta.
Nasa's robotic satellite sent data early on Sunday confirming it was circling the 530km-wide body.
The probe has taken almost four years to get to Vesta and will spend the next year studying the huge rock before moving on to the "dwarf planet" Ceres.

Asteroid Vesta looks like a punctured football, the result of a colossal collision sometime in its past that knocked off its south polar region.

"Today, we celebrate an incredible exploration milestone as a spacecraft enters orbit around an object in the main asteroid belt for the first time," Nasa Administrator Charles Bolden said in a statement.
"Dawn's study of the asteroid Vesta marks a major scientific accomplishment and also points the way to the future destinations where people will travel in the coming years. President Obama has directed Nasa to send astronauts to an asteroid by 2025, and Dawn is gathering crucial data that will inform that mission."

Vesta was discovered in 1807, the fourth asteroid to be identified in the great belt of rocky debris orbiting between Mars and Jupiter.
At the time, its great scale meant it was designated as another planet but it later lost this status as researchers learnt more about the diversity of objects in the Solar System.

Dawn's encounter is occurring about 188 million km (117 million miles) from Earth.
The probe is propelled by an ion engine and engineers put the spacecraft on a course to be captured in the gravitational field of Vesta.
They cannot say precisely when that happened; it will have depended on the asteroid's mass - and that property is something Dawn will determine during its stay.

Initially, Dawn will be orbiting at a distance of several thousand km from the asteroid, but this distance will be reduced over time.
Mission scientists hope to get within 200km of the surface but the team do not intend to take any unnecessary risks.
"We would like to get as low as possible but if we crash Dawn, Nasa would understandably be very angry at us," Principal Investigator Chris Russell told BBC News.

Asteroids can tell us about the earliest days of the Solar System. These wandering rocks are often described as the rubble that was left over after the planets proper had formed.

Vesta and Ceres should make for interesting subjects. They are both evolved bodies - objects that have heated up and started to separate into distinct layers.
"We think that Vesta has a metal core in the centre - an iron core - and then silicate rock around it," explained Dr Russell.
"And then, sometime in its history, it got banged on the bottom and a lot of material was liberated. Some of this material gets pulled into the Earth's atmosphere. One in 20 meteorites seen to fall to Earth has been identified with Vesta," he added.

Ceres, which, at 950km in diameter, is by far the largest and most massive body in the asteroid belt, probably did not evolve as much as Vesta.
Scientists think it likely that it retains a lot of water, perhaps in a band of ice deep below the surface.

Dawn's quest at Vesta over the coming months will be to map the asteroid's surface.
The probe carries instruments to detect the mineral and elemental abundances in its rocks. It will be looking for evidence of geological processes such as mountain building and rifting. The team is keen to understand how Vesta's surface has been remodelled over time by impacts and even lava flows.

http://www.bbc.co.uk/news/science-environment-14160135

 

[eburacum]

If there is water there and enough carbon, nitrogen and the other elements required for life (which seems likely) this asteroid may make a useful location for a colony.

There are problems, though - the low gravity (about 0.02 g), which may pose a health risk (no-one really knows, as no-one has ever lived in 1/50 gee before).
Low gravity also makes it tricky to land there-with almost no gravity to pull a passing spacecraft into orbit, landing there is expensive in terms of delta vee.