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Earth has been hit 566 times over 20 years

This map uses data gathered from 1994-2013 and shows where small asteroids hit Earth's atmosphere and produced very bright meteors, technically called 'bolides' and commonly referred to as 'fireballs'. The objects ranged in size from about 1 metre (3 feet) to almost 20 metres (60 feet).

This map uses data gathered from 1994-2013 and shows where small asteroids hit Earth’s atmosphere and produced very bright meteors, technically called ‘bolides’ and commonly referred to as ‘fireballs’. The objects ranged in size from about 1 metre (3 feet) to almost 20 metres (60 feet).

A map released by NASA’s Near Earth Object (NEO) Program reveals that small asteroids frequently enter and disintegrate in Earth’s atmosphere with random spread around the globe.

Released to the scientific community, the map visualises data gathered by U.S. government sensors from 1994 to 2013. (‘Sensors’ probably means, or at least includes, spy satellites. Ed.)

The data indicate that Earth’s atmosphere was hit by small asteroids, resulting in a bolide (or fireball), on 556 separate occasions in a 20-year period.

Almost all asteroids of this size disintegrate in the atmosphere and are usually harmless. The notable exception was the Chelyabinsk event, which was the largest asteroid to hit Earth in this period.

Trail left by the Chelyabinsk meteor.

Trail left by the Chelyabinsk meteor.

The new data could help scientists better refine estimates of the distribution of the sizes of NEOs including larger ones that could pose a danger to Earth.

Finding and characterising hazardous asteroids to protect our home planet is a high priority for NASA, and is one of the reasons the agency has increased by a factor of 10 investments in asteroid detection, characterisation and mitigation activities over the last five years.

In addition, NASA has aggressively developed strategies and plans with its partners in the U.S. and abroad to detect, track and characterise NEOs.

These activities also will help identify NEOs that might pose a risk of Earth impact, and further help inform developing options for planetary defence.

The public can help participate in the hunt for potentially hazardous Near Earth Objects through the Asteroid Grand Challenge, which aims to create a plan to find all asteroid threats to human populations and know what to do about them.

NASA is also pursuing an Asteroid Redirect Mission (ARM) which will identify, redirect and send astronauts to explore an asteroid.

Among its many exploration goals, the mission could demonstrate basic planetary defence techniques for asteroid deflection.

Adapted from information issued by NASA’s Jet Propulsion Laboratory. Chelyabinsk meteor image courtesy Alex Alishevskikh under CC. Map courtesy Planetary Science.

Asteroids are pounding a pulsar

SCIENTISTS USING CSIRO’s Parkes telescope and another telescope in South Africa have found evidence that a tiny star called PSR J0738-4042 is being pounded by asteroids – large lumps of rock in space.

“One of these rocks seems to have had a mass of about a billion tons,” CSIRO astronomer and member of the research team Dr Ryan Shannon said.

PSR J0738-4042 lies 37,000 light-years from Earth in the constellation of Puppis. The environment around the star is especially harsh, full of radiation and violent winds of particles.

“If a large rocky object can form here, planets could form around any star. That’s exciting,” Dr Shannon said.

The star is a special one, a ‘pulsar’ that emits a beam of radio waves. As it spins, its radio beam flashes over Earth again and again with the regularity of a clock.

An artist's impression of an asteroid breaking up

An artist’s impression of an asteroid breaking up. Credit: NASA/JPL-Caltech

Formed from shattered remains

In 2008 Dr Shannon and a colleague predicted how an infalling asteroid would affect a pulsar. It would, they said, alter the slowing of the pulsar’s spin rate and the shape of the radio pulse that we see on Earth.

“That is exactly what we see in this case,” Dr Shannon said. “We think the pulsar’s radio beam zaps the asteroid, vaporising it. But the vaporised particles are electrically charged and they slightly alter the process that creates the pulsar’s beam.”

Asteroids circling a pulsar could have been formed by the remains of the exploding star that produced the pulsar itself, the scientists say. The material blasted out from the explosion could fall back towards the pulsar, developing into a swirling cloud of dusty debris that circles it. Astronomers call it a ‘disc’.

Not the only one

Astronomers have found a dust disc around another pulsar called J0146+61.

Parkes radio telescope

The CSIRO’s Parkes radio telescope. Photo courtesy Shaun Amy.

“This sort of dust disc could provide the ‘seeds’ that grow into larger asteroids,” said Paul Brook, a PhD student co-supervised by the University of Oxford and CSIRO who led the study of PSR J0738-4042.

In 1992 two planet-sized objects were found around a pulsar called PSR 1257+12. But these were probably formed by a different mechanism, the astronomers say.

The new study has been published in The Astrophysical Journal Letters, a leading journal of astronomical research.

Adapted from information issued by CSIRO.

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NASA to keep watch on asteroid

2012 DA14 trajectory past Earth

Asteroid 2012 DA14 will pass close to the Earth on February 15 (February 16, Australian time) – so close in fact, that it will be nearer to us than the ring of communications and weather satellites that orbit our planet.

THE RECORD-SETTING CLOSE APPROACH of an asteroid on February 15 (early morning February 16, Australian time) is an exciting opportunity for scientists, and a research team will use US National Radio Astronomy Observatory (NRAO) and NASA telescopes to gain a key clue that will help them predict the future path of this nearby cosmic neighbour.

A 45-metre-wide asteroid called 2012 DA14, discovered just a year ago, will pass only 28,000 kilometres above the Earth’s surface. That’s closer than the geosynchronous communication and weather satellites. While the object definitely will not strike the Earth, this is a record close approach for an object of this size. Astronomers around the world are preparing to take advantage of the event to study the asteroid.

A team including NRAO astronomer Michael Busch will use a novel observing technique to determine which way the space rock is spinning as it speeds on its orbit through the solar system. The direction of its spin is an important factor in predicting how the object’s orbit will change over time.

“Knowing the direction of spin is essential to accurately predicting its future path, and thus determining just how close it will get to Earth in the coming years,” Busch said.

Radar observations

Busch’s team will use the Karl G. Jansky Very Large Array (VLA) and the Very Long Baseline Array (VLBA) antennae at Pie Town and Los Alamos, New Mexico, along with a radar on NASA’s 70-metre-diameter antenna at Goldstone, California.

The Goldstone antenna will transmit a powerful beam of radio waves toward the asteroid, and NRAO’s New Mexico antennae will receive the waves reflected from the asteroid’s surface.

Because of the asteroid’s uneven surface and the different reflectivity of portions of the surface, the reflected radar signal will have a characteristic signature, or ‘speckles,’ as seen from Earth. By measuring which antenna in a widely-separated pair receives the speckle pattern first, the astronomers can learn which way the asteroid is spinning.

This way of using the telescopes is significantly different to their normal astronomical observing, and the research team has developed special techniques for processing the data.

Yarkovsky Effect graphic

How the Yarkovsky Effect slows an asteroid’s orbital motion; opposite rotation direction would speed up the orbital motion.

Asteroid’s ‘afternoon’ heat

How does this tell anything about the asteroid’s orbital changes? Just as the afternoon is the warmest part of the day on Earth, the space rock develops a warm region that radiates infrared light in its maximum amount during ‘afternoon’ on the asteroid. That outgoing infrared radiation provides a gentle but firm jet-like push to the asteroid.

The direction of the asteroid’s spin determines whether ‘afternoon’ is either forward or rearward of its direction of motion.

If the hot spot is forward of the direction of motion, the infrared push will slow the asteroid’s orbital speed, and if the hot spot is rearward of the direction of motion, it will speed up the orbital motion. This effect, over time, can make a significant change in the orbit. This is called the Yarkovsky Effect, after the engineer who first identified it.

“When the asteroid passes close to the Earth or another large body, its orbit can be changed quickly by the gravitational effect of the larger body, but the Yarkovsky Effect, though smaller, is at work all the time,” Busch said.

Adapted from information issued by the National Radio Astronomy Observatory. Yarkovsky Effect graphic by Alexandra Bolling, NRAO / AUI / NSF. Orbit graphic by P. Chodas, NASA / JPL.

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Sentinel telescope to protect Earth

IN A PRESS CONFERENCE at the California Academy of Sciences Thursday Morning (US time), the B612 Foundation unveiled its plans to build, launch, and operate the first privately funded deep space mission.

Called Sentinel, the a space telescope will be placed in orbit around the Sun, ranging up to 270 million kilometres from Earth, for a mission of discovery and mapping.

The Foundation leadership and technical team includes some of the most experienced professionals in the world to lead this effort.

“The orbits of the inner Solar System where Earth lies are populated with a half million asteroids larger than the one that struck Tunguska (June 30, 1908), and yet we’ve identified and mapped only about one percent of these asteroids to date, said Ed Lu, space shuttle, Soyuz, and International Space Station astronaut, now Chairman and CEO of the B612 Foundation.

The asteroid that entered Earth’s atmosphere over Tunguska, Russia, was only about 40 metres across (less than the length of an Olympic swimming pool) yet destroyed an unpopulated area roughly the size of the San Francisco Bay area.

“During its 5.5-year mission survey time, Sentinel will discover and track half a million near Earth asteroids, creating a dynamic map that will provide the blueprint for future exploration of our Solar System, while protecting the future of humanity on Earth,” says Lu.

Trees flattened at Tunguska in 1908

A 40-metre-wide meteroid exploded in the air over Tunguska, Russia, in 1908, flattening over 2,000 square kilometres of forest.

Spotting dangerous asteroids

Asteroids are a scientific and economic opportunity in that they contain the original building blocks of the Solar System. They are targets for future human exploration, and may contain valuable raw materials for mining.

But these asteroids are also a threat in that they can pose great risk to humanity here on Earth. Taking advantage of these opportunities and dealing with these threats require not only knowing where each of these individual asteroids is now, but also projecting where they will be in the future.

“For the first time in history, B612’s Sentinel mission will create a comprehensive and dynamic map of the inner Solar Systemin which we live—providing vital information about who we are, who are our neighbours, and where we are going,” says Rusty Schweickart, Chairman Emeritus of B612, and Apollo 9 astronaut.

Diagram of the Sentinel telescope

The solar-powered Sentinel telescope will be equipped with a special camera to spot asteroids.

“We will know which asteroids will pass close to Earth and when, and which, if any of these asteroids actually threaten to collide with Earth,” adds Schweickart. “The nice thing about asteroids is that once you’ve found them and once you have a good solid orbit on them you can predict a hundred years ahead of time whether there is a likelihood of an impact with the Earth.”

Sentinel to launch in five years

Advances in space technology, including advances in infrared sensing and on-board computing, as well as low-cost launch systems, have opened up a new era in exploration where private organisations can now carry out grand and audacious space missions previously only achievable by governments.

The B612 Foundation is working with Ball Aerospace, Boulder, Colorado, which has designed and will be building the Sentinel Infrared (IR) Space Telescope with the same expert team that developed the Spitzer and Kepler space telescopes. It will take approximately five years to complete development and testing to be ready for launch in 2017-2018. The launch vehicle of choice is the SpaceX Falcon9.

Sentinel will scan the entire night half of the sky every 26 days to identify every moving object, with repeated observations in subsequent months. Data collected by Sentinel will be sent back to the Earth via NASA’s Deep Space Network, which also will be used for tracking and navigation.

More information: B612 Foundation

Adapted from information issued by the B612 Foundation.

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Giant asteroid’s secrets revealed

View of Vesta's southern regions

NASA's Dawn mission has begun to reveal Vesta's complex history. The 110-kilometre-wide dwarf planet is the second-largest body in the asteroid belt.

NASA’s DAWN SPACECRAFT has provided researchers with the first close-up analysis of the giant asteroid Vesta, yielding new insights into its creation and kinship with terrestrial planets and Earth’s Moon.

Vesta now has been revealed as a special fossil of the early Solar System with a more varied, diverse surface than originally thought. Scientists have confirmed a variety of ways in which Vesta more closely resembles a small planet or Earth’s Moon than another asteroid.

“Dawn’s visit to Vesta has confirmed our broad theories of this giant asteroid’s history, while helping to fill in details it would have been impossible to know from afar,” said Carol Raymond, deputy principal investigator at NASA’s Jet Propulsion Laboratory in Pasadena, Calif.

“Dawn’s residence at Vesta of nearly a year has made the asteroid’s planet-like qualities obvious and shown us our connection to that bright orb in our night sky.”

Complex history

Scientists now see Vesta as a layered, planetary building block with an iron core—the only one known to survive the earliest days of the Solar System.

The asteroid’s geologic complexity can be attributed to a process that separated the asteroid into a crust, mantle and iron core with a radius of approximately 110 kilometres about 4.56 billion years ago. The terrestrial planets and Earth’s Moon formed in a similar way.

Graphic showing size comparisons of Mars, Mercury, the Moon and Ceres

Family history: Mars, Mercury, Earth's Moon and the dwarf planet Ceres.

Dawn observed a pattern of minerals exposed by deep gashes formed by space rock impacts, which may support the idea the asteroid once had a subsurface magma ocean.

A magma ocean occurs when a body undergoes almost complete melting, leading to layered building blocks that can form planets. Other bodies with magma oceans ended up becoming parts of Earth and other planets.

Meteorite matches

Data also confirm that a distinct group of meteorites found on Earth did, as theorised, originate from Vesta. The signatures of pyroxene—an iron- and magnesium-rich mineral—in those meteorites match those of rocks on Vesta’s surface.

These objects account for about 6 percent of all meteorites seen falling on Earth.

Three slices of meteorites

Chunks of Vesta have fallen on Earth as meteorites. These are slices of some of them.

This makes the asteroid one of the largest single sources for Earth’s meteorites. The finding also marks the first time a spacecraft has been able to visit the source of samples after they were identified on Earth.

Similarity to moons

Scientists now know Vesta’s topography is quite steep and varied. Some craters on Vesta formed on very steep slopes and have nearly vertical sides, with landslides occurring more frequently than expected.

Another unexpected finding was that the asteroid’s central peak in the Rheasilvia basin in the southern hemisphere is much higher and wider, relative to its crater size, than the central peaks of craters on bodies like our Moon.

Vesta also bears similarities to other low-gravity worlds like Saturn’s small icy moons, and its surface has light and dark markings that don’t match the predictable patterns on Earth’s Moon.

“We know a lot about the Moon and we’re only coming up to speed now on Vesta,” said Vishnu Reddy, a framing camera team member at the Max Planck Institute for Solar System Research in Germany and the University of North Dakota in Grand Forks.

Topographic map of Vesta

Vesta was clobbered by impacts that left huge scars. The largest is called Rheasilvia.

“Comparing the two gives us two storylines for how these fraternal twins evolved in the early Solar System.”

A battered world

Dawn has revealed details of ongoing collisions that battered Vesta throughout its history. Scientists now can date the two giant impacts that pounded Vesta’s southern hemisphere and created the basin Veneneia approximately 2 billion years ago and the Rheasilvia basin about 1 billion years ago. Rheasilvia is the largest impact basin on Vesta.

“The large impact basins on the Moon are all quite old,” said David O’Brien, a Dawn participating scientist from the Planetary Science Institute in Tucson, Arizona. “The fact that the largest impact on Vesta is so young was surprising.”

Launched in 2007, Dawn began exploring Vesta in mid-2011. The spacecraft will depart Vesta on August 26 for its next study target, the dwarf planet Ceres, in 2015.

More information:

NASA’s Dawn mission page

JPL’s Dawn mission page

Adapted from information issued by NASA / JPL-Caltech. Images courtesy NASA / JPL-Caltech / UCLA / University of Tennessee / MPS / DLR / IDA / PSI.

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Earth’s other moons

EARTH USUALLY HAS MORE THAN ONE MOON, according to a team of astronomers from the University of Helsinki, the Paris Observatory and the University of Hawaii at Manoa.

Our 3,400-kilometre-diameter Moon, so beloved by poets, artists and romantics, has been orbiting Earth for over 4 billion years. Its much smaller cousins, dubbed “minimoons,” are thought to be only metres across and to usually orbit our planet for less than a year before resuming their previous lives as asteroids orbiting the Sun.

Mikael Granvik (formerly at UH Manoa and now at Helsinki), Jeremie Vaubaillon (Paris Observatory) and Robert Jedicke (UH Manoa) calculated the probability that at any given time Earth has more than one moon. They used a supercomputer to simulate the passage of 10 million asteroids past Earth. They then tracked the trajectories of the 18,000 objects that were captured by Earth’s gravity.

They concluded that at any given time there should be at least one asteroid with a diameter of at least one metre orbiting Earth. Of course, there may also be many smaller objects orbiting Earth, too.

Captured by Earth’s gravity

According to the simulation, most asteroids that are captured by Earth’s gravity would not orbit Earth in neat circles. Instead, they would follow complicated, twisting paths. This is because a minimoon would not be tightly held by Earth’s gravity, so it would be tugged into a crazy pathby the combined gravity of Earth, the Moon and the Sun.

Path of a simulated minimoon

The path of a simulated minimoon that is temporarily captured by Earth. The object approaches Earth from the right and finally escapes capture along the red path to the upper right. The size of Earth and the Moon are not to scale but the size of the minimoon’s path is to scale in the Earth-Moon system. Inset: Radar image of near-Earth asteroid 1999. This 3.5-km-wide asteroid is more than 1,000 times larger than the biggest minimoons, but it shows the irregular shape and expected of minimoons.

A minimoon would remain captured by Earth until one of those tugs breaks the pull of Earth’s gravity, and the Sun once again takes control of the object’s trajectory. While the typical minimoon would orbit Earth for about nine months, some of them could orbit our planet for decades.

“This was one of the largest and longest computations I’ve ever done,” said Vaubaillon. “If you were to try to do this on your home computer, it would take about six years.”

In 2006, the University of Arizona’s Catalina Sky Survey discovered a minimoon about the size of a car. Known by the unimaginative designation 2006 RH120, it orbited Earth for less than a year after its discovery, then resumed orbiting the Sun.

“Minimoons are scientifically extremely interesting,” said Jedicke. “A minimoon could someday be brought back to Earth, giving us a low-cost way to examine a sample of material that has not changed much since the beginning of our Solar System over 4.6 billion years ago.”

The team used the Jade supercomputer at the National Computer Centre for Higher Education (Centre Informatique National de l’Enseignement Supérieur, or CINES) at Montpelier, France.

The team’s paper, “The population of natural Earth satellites,” appears in the March issue of the journal Icarus.

Adapted from information issued by the University of Hawaii at Manoa. 1999 JM8 image made with NASA’s Goldstone Solar System Radar in California and the Arecibo Observatory in Puerto Rico by a team of astronomers led by Dr. Lance Benner of NASA’s Jet Propulsion Laboratory in Pasadena, California

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Space Rock – The movie

SCIENTISTS WORKING WITH the 70-metre-wide Deep Space Network antenna at Goldstone, California, have generated a short movie clip of asteroid 2005 YU55. The images used to generate the movie are the highest-resolution ever generated by radar of a near-Earth object.

Each of the six frames required 20 minutes of data collection by the Goldstone radar. At the time, 2005 YU55 was approximately 1.38 million kilometres away from Earth. Resolution is 4 metres per pixel.

“By animating a sequence of radar images, we can see more surface detail than is visible otherwise,” said radar astronomer Lance Benner, the principal investigator for the 2005 YU55 observations, from NASA’s Jet Propulsion Laboratory.

“The animation reveals a number of puzzling structures on the surface that we don’t yet understand. To date, we’ve seen less than one half of the surface, so we expect more surprises.”

No effect on Earth

The trajectory of asteroid 2005 YU55 is well understood. At the point of closest approach it was no closer than (324,600 kilometres, as measured from the centre of Earth.

The gravitational influence of the asteroid will have had no detectable effect on anything here on Earth, including our planet’s tides or tectonic plates.

Although 2005 YU55 is in an orbit that regularly brings it to the vicinity of Earth (and Venus and Mars), the 2011 encounter with Earth is the closest this space rock has come for at least the last 200 years.

The last time an asteroid as big came as close to Earth was in 1976, although astronomers did not know about the flyby at the time. The next known approach of an asteroid this large will be in 2028.

Adapted from information issued by NASA / JPL-Caltech.

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Earth to be buzzed by asteroid

Radar image of asteroid 2005 YU55

This radar image of asteroid 2005 YU55 was generated from data taken in April of 2010 by the Arecibo Radar Telescope in Puerto Rico. The 400-metre-wide space rock will zip past Earth on November 9 (Sydney time).

EARTH IS GOING TO BUZZED by a 400-metre-wide asteroid next week, in a near miss that will bring the space rock to within a distance closer than the Moon.

NASA scientists will track the object, known as 2005 YU55, with antennae of the agency’s Deep Space Network at Goldstone, California, as it flies past Earth on November 9 (Sydney time).

Scientists are treating the flyby as a ‘target of opportunity’, giving instruments on ‘spacecraft Earth’ the chance to scan it during the close pass.

Tracking of the aircraft carrier-sized asteroid will begin on November 4 using Goldstone’s huge 70-metre-wide Deep Space Network antenna, and last for about two hours. Goldstone will continue to track the asteroid for at least four hours each day through to November 10.

Radar observations from the Arecibo Planetary Radar Facility in Puerto Rico will begin on November 8, with the asteroid due to make its closest approach to Earth at 10:38am on November 9, Sydney time.

No danger

The trajectory of asteroid 2005 YU55 is well understood. At the point of closest approach, it will be no closer than 324,600 kilometres or 0.85 the distance from the moon to Earth.

The gravitational influence of the asteroid will have no detectable effect on anything here on Earth, including our planet’s tides or tectonic plates.

Although 2005 YU55 is in an orbit that regularly brings it to the vicinity of Earth (and Venus and Mars), the 2011 encounter with Earth is the closest this space rock has come for at least the last 200 years.

Goldstone and Arecibo dishes

NASA's 70-metre-wide dish at Goldstone in California (left) and the US National Science Foundation's 305-metre-wide dish at Arecibo Observatory in Puerto Rico, will track the asteroid as it passes Earth.

During tracking, scientists will use the Goldstone and Arecibo antennas to bounce radio waves off the space rock. Radar echoes returned will be collected and analysed.

NASA scientists hope to obtain images of the asteroid from Goldstone as fine as about 2 metres per pixel. This should reveal a wealth of detail about the asteroid’s surface features, shape, dimensions and other physical properties (see “Radar Love”).

Arecibo radar observations of asteroid 2005 YU55 made in 2010 show it to be approximately spherical in shape. It is slowly spinning, with a rotation period of about 18 hours. The asteroid’s surface is darker than charcoal at optical wavelengths.

Spaceguard

The last time a space rock as big came as close to Earth was in 1976, although astronomers did not know about the flyby at the time. The next known approach of an asteroid this large will be in 2028.

NASA detects, tracks and characterises asteroids and comets passing close to Earth using both ground- and space-based telescopes. The Near-Earth Object Observations Program, commonly called “Spaceguard,” discovers these objects, characterises a subset of them, and plots their orbits to determine if any could be potentially hazardous to our planet.

More information about asteroids and near-Earth objects.

More information about asteroid radar research.

More information about the Deep Space Network.

Adapted from information issued by NASA / JPL. Images courtesy NASA / Cornell / Arecibo, and H. Schweiker / WIYN and NOAO / AURA / NSF.

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Latest Dawn image of Vesta

Dawn image of the surface of the asteroid Vesta

Craters large and small litter the surface of the 530-kilometre-wide asteroid Vesta. This image was taken by the Dawn's spacecraft's framing camera. Dawn will spend the next 12 months in orbit around Vesta.

NASA’S DAWN SPACECRAFT obtained this image of Vesta with its framing camera on July 31, 2011. It was taken from a distance of about 3,700 kilometres from the giant asteroid.

Vesta is one of the largest of the asteroids, and orbits the Sun in the main asteroid belt between Mars and Jupiter.

The smallest visible detail, which is about 2 pixels, corresponds to roughly 70 metres.

Dawn arrived at Vesta on July 16 after a journey of almost four years. It is now in orbit around the 530-kilometre-wide asteroid and will spend the next 12 months investigating it.

At the end of those 12 months, it will depart Vesta and voyage to the even-larger main belt body, the dwarf planet Ceres, and spend a further 12 months studying that object.

The aim of the Dawn mission is to shed light on the origins of the Sun and the planets by examining these two asteroids, which are thought to be amongst the oldest surviving bodies in the Solar System.

More information:

First close-up images from Vesta

NASA’s Dawn mission pages

Adapted from information issued by NASA / JPL-Caltech / UCLA / MPS / DLR / IDA.

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Vesta vistas streaming in

Full-frame image of Vesta

NASA's Dawn spacecraft obtained this image of the giant asteroid Vesta with its framing camera on July 24, 2011. It was taken from a distance of about 5,200 kilometres. Dawn will spend a year orbiting the body. After that, the next stop on its itinerary will be an encounter with the dwarf planet Ceres.

  • Vesta is one of the largest asteroids
  • Dawn mission will spend a year investigating it
  • First close-up images now coming in

AFTER TRAVELLING NEARLY FOUR YEARS and 2.8 billion kilometres, NASA’s Dawn spacecraft has been captured by the Vesta’s gravity. The giant asteroid and its new companion are currently approximately 184 million kilometres from Earth.

The first spacecraft to orbit an object in the main asteroid belt, Dawn is now spiralling down towards its first of four intensive science orbits. That initial orbit of the rocky world—to begin on August 11, at an altitude of nearly 2,700 kilometres—will provide in-depth analysis of the asteroid.

Vesta, 530 kilometres wide, is the brightest object in the asteroid belt as seen from Earth and is thought to be the source of a large number of meteorites that fall to Earth.

Snowman craters on Vesta

A set of three craters, informally nicknamed 'Snowman' by the camera's team members, is located in the northern hemisphere of Vesta.

Craters on Vesta

Various craters are visible in this image of part of the southern equatorial region of the giant asteroid Vesta.

The smallest rocky ‘planet’

Images from Dawn’s framing camera, taken for navigation purposes and as preparation for scientific observations, are revealing the first surface details of the giant asteroid. These images go all the way around Vesta, since the giant asteroid turns on its axis once every five hours and 20 minutes.

“Now that we are in orbit around one of the last unexplored worlds in the inner Solar System, we can see that it’s a unique and fascinating place,” said Marc Rayman, Dawn’s chief engineer and mission manager at NASA’s Jet Propulsion Laboratory.

Download a Vesta wallpaper image, 1024 x 1024 pixels.

“We have been calling Vesta the smallest terrestrial planet,” said Chris Russell, Dawn’s principal investigator at UCLA. “The latest imagery provides much justification for our expectations.”

“They show that a variety of processes were once at work on the surface of Vesta and provide extensive evidence for Vesta’s planetary aspirations.”

Here’s a short video showing the different faces of Vesta as it rotates:

“The new observations of Vesta are an inspirational reminder of the wonders unveiled through ongoing exploration of our Solar System,” said Jim Green, planetary division director at NASA Headquarters in Washington.

Dawn launched in September 2007. Following a year at Vesta, the spacecraft will depart in July 2012 for Ceres, where it will arrive in 2015.

More information: NASA’s Dawn mission pages

Adapted from information issued by NASA. Images courtesy NASA / JPL-Caltech / UCLA / MPS / DLR / IDA.

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