NASA Spacecraft Arrives at Arizona-Size Asteroid Next Week
by Mike Wall, SPACE.com Senior Writer
Date: 05 July 2011 Time: 03:28 PM ET
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| NASA's Dawn spacecraft obtained this image on its approach to the protoplanet Vesta, the second-most massive object in the main asteroid belt. The image was obtained on June 20, 2011. CREDIT: NASA/JPL-Caltech/ UCLA/MPS/DLR/PSI |
A NASA spacecraft is just 11 days away from a historic rendezvous with an asteroid the size of Arizona.
NASA's Dawn probe should enter into orbit around Vesta on July 16, becoming the first spacecraft to visit the 330-mile-wide (530-kilometer) space rock — the second-largest object in the main asteroid belt between Mars and Jupiter. Dawn is expected to spend a year studying the space rock from above, marking the first time a spacecraft has ever made an extended visit to a large asteroid.
Scientists hope Dawn's mission will help them learn about the early days of the solar system and the processes that formed and shaped rocky planets like Earth and Mars.
"Bodies like Vesta are building blocks," Dawn principal investigator Christopher Russell of UCLA told reporters in a recent briefing. "So we're going back and doing some sort of investigation into our roots, the roots of the solar system."
A long journey
Dawn is now in the home stretch of a nearly four-year cosmic chase. The probe launched in September 2007 and has logged about 1.7 billion miles (2.7 billion km) during its travels. As of Friday (July 1), Dawn had closed to within 53,400 miles (86,000 km) of Vesta, researchers said.
Dawn will be just 9,900 miles (16,000 km) from Vesta when the space rock's gravity captures the probe on July 16. At that point, Dawn and Vesta will both be about 117 million miles (188 million km) from Earth.
The capture shouldn't be a dramatic, nail-biting affair punctuated by last-minute thruster burns. Dawn has been using its low-thrust ion propulsion system to close in on Vesta slowly but surely, and it should slide nicely into orbit on July 16.
The spacecraft will begin its science operations in early August, researchers said.
Studying a protoplanet
Vesta is so large that many scientists classify it as a protoplanet. The object was well on its way to becoming a full-fledged rocky planet long ago, scientists said, but circumstances intervened.
"The formation of Jupiter started stirring up that region of the asteroid belt and preventing materials from coming together any longer," Russell said. [Photos: Asteroids in Deep Space]
So Vesta is a sort of time capsule, preserving some record of how the solar system came together 4.5 billion years ago.
"As we explore Vesta, we take a virtual journey back in time to the beginning of the solar system," said Carol Raymond, Dawn deputy principal investigator at NASA's Jet Propulsion Laboratory (JPL) in Pasadena, Calif.
During its year at Vesta, Dawn will map the giant asteroid's cratered surface fully, study its composition and investigate its geological history. It will do this from several different orbits, ranging from 1,700 miles (2,700 km) above Vesta to just 120 miles (200 km), researchers said.
Massive asteroid hurtling towards Earth (but don't worry, scientists say it will just miss us)
Last updated at 4:36 PM on 6th May 2011
- Space rock YU55 will hurtle past our planet at a distance of just 201,700 miles on November 8
A massive asteroid will fly within the moon's orbit narrowly missing Earth later this year.
The space rock, called YU55, will hurtle past our planet at a distance of just 201,700 miles during its closest approach on November 8.
That is closer to Earth than the moon, which orbits 238,857miles away on average.
With a width of some 400metres and weighing 55million tons, YU55 will be the largest object to ever approach Earth so close.
With a width of some 400metres and weighing 55million tons, YU55 will be the largest object to ever approach Earth so close.
Incoming: YU55 was imaged by the Arecibo Radar Telescope in Puerto Rico in April last year. At the time this fuzzy picture was taken, the asteroid was 1.5million miles from Earth
Nasa spokesman Don Yeomans said: 'On November 8, asteroid YU55 will fly past Earth and at its closest approach point will be about 325,000kms away.
'This asteroid is about 400 metres wide - the largest space rock we have identified that will come this close until 2028.'
HOW TO DEFLECT AN ASTEROID
Scientists have come up with a number of different ways of deflecting an incoming asteroid from its path, some more realistic than others.
Here are a few of the best ideas:
- Nuclear blast: A large nuclear explosion on an asteroid might be enough to deflect an asteroid but has significant political and ethical problems. And what if we just blew it into smaller pieces?
- Using mirrors: A fleet of spacecraft carrying light-reflecting mirrors might be able to vaporise the asteroid's surface using the Sun's rays. The gases from its surface would create a tiny amount of thrust - enough to divert it.
- Gravity tractor: Crashing a spacecraft into the asteroid would certainly be the cheapest option. The ship's own tiny gravity would then help move the asteroid's path. But this option would take a long time to make a difference.
Despite YU55's close proximity to Earth, its gravitational pull on our planet will be 'immeasurably miniscule'.
Mr Yeomans added: 'During its closest approach, its gravitational effect on the Earth will be so miniscule as to be immeasurable. It will not affect the tides or anything else.'
It is, however, still officially labelled a 'potentially hazardous object' - if it was to hit Earth, it would exert a force the equivalent of 65,000 atomic bombs and leave a crater six miles wide and 2,000ft deep.
YU55 was discovered by Robert McMillan, head of the Nasa-funded Spacewatch Program at the University of Arizona, Tucson in December 2005.
It orbits the sun once every 14 years but will not collide with Earth for at least a century.
'YU55 poses no threat of an Earth collision over, at the very least, the next 100 years,' Mr Yeomans said.
Scientists around the world have long been discussing ways of deflecting potentially hazardous asteroids to prevent them hitting Earth.
One of the more popular methods is to detonate a nuclear warhead on an approaching asteroid to deflect it from its orbital path.
Last year, physicist David Dearborn of the Lawrence Livermore National Laboratory in the US argued that nuclear weapons could be the best strategy for avoiding an asteroid impact - especially for large asteroids and with little warning time.
Read more: http://www.dailymail.co.uk/sciencetech/article-1383778/YU55-asteroid-hurtling-Earth-scientists-say-just-miss-us.html#ixzz1RLIzYGHy
Published May 09, 2011
| Space.com
Arecibo Observatory/Michael Nolan
The near-Earth asteroid 2005 YU55 — on the list of potentially dangerous asteroids — was observed with the Arecibo Telescope's planetary radar on April 19, 2010, when it was about 1.5 million miles from Earth.
An asteroid the size of an aircraft carrier will come closer to Earth this autumn than our own moon does, causing scientists to hold their breath as it zooms by. But they'll be nervous with excitement, not with worry about a possible disaster.
There's no danger of an impact when the asteroid 2005 YU55 makes its close flyby Nov. 8, coming within 201,700 miles (325,000 kilometers) of Earth, scientists say.
"While near-Earth objects of this size have flown within a lunar distance in the past, we did not have the foreknowledge and technology to take advantage of the opportunity," Barbara Wilson, a scientist at NASA's Jet Propulsion Laboratory in Pasadena, Calif., said in a statement. "When it flies past, it should be a great opportunity for science instruments on the ground to get a good look." [Photos: Asteroids in Deep Space]
Getting to know YU55
Asteroid 2005 YU55 is about 1,300 feet (400 meters) wide. It was discovered in December 2005 by the Spacewatch program at the University of Arizona in Tucson.
Because of the asteroid’s size and orbital characteristics, astronomers have flagged 2005 YU55 as potentially dangerous down the road. But the upcoming encounter is no cause for alarm, researchers said.
"YU55 poses no threat of an Earth collision over, at the very least, the next 100 years," said Don Yeomans, manager of NASA's Near-Earth Object Program Office at JPL. "During its closest approach, its gravitational effect on the Earth will be so minuscule as to be immeasurable. It will not affect the tides or anything else." [5 Reasons to Care About Asteroids]
This round space rock has been in astronomers' cross hairs before. In April 2010, astronomers at the National Science Foundation's Arecibo Observatory in Puerto Rico generated some ghostly radar images of 2005 YU55 when the asteroid was about 1.5 million miles (2.3 million km) from Earth.
But those pictures had a resolution of just 25 feet (7.5 meters) per pixel. The November close pass should provide some sharper images.
"When 2005 YU55 returns this fall, we intend to image it at 4-meter resolution [13 feet] with our recently upgraded equipment at the Deep Space Network at Goldstone, California," said JPL radar astronomer Lance Benner. "Plus, the asteroid will be seven times closer. We're expecting some very detailed radar images."
So they're looking forward to the encounter, which could help them learn more about big space rocks.
Asteroid Defined
Asteroids are rocky and metallic objects that orbit the Sun but are too small to be considered planets. They are known as minor planets. Asteroids range in size from Ceres, which has a diameter of about 1000 km, down to the size of pebbles.
Sixteen asteroids have a diameter of 240 km or greater. They have been found inside Earth's orbit to beyond Saturn's orbit. Most, however, are contained within a main belt that exists between the orbits of Mars and Jupiter. Some have orbits that cross Earth's path and some have even hit the Earth in times past. One of the best preserved examples is Barringer Meteor Crater near Winslow, Arizona.
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Asteroids are material left over from the formation of the solar system. One theory suggests that they are the remains of a planet that was destroyed in a massive collision long ago. More likely, asteroids are material that never coalesced into a planet. In fact, if the estimated total mass of all asteroids was gathered into a single object, the object would be less than 1,500 kilometers (932 miles) across -- less than half the diameter of our Moon.
Much of our understanding about asteroids comes from examining pieces of space debris that fall to the surface of Earth. Asteroids that are on a collision course with Earth are called meteoroids. When a meteoroid strikes our atmosphere at high velocity, friction causes this chunk of space matter to incinerate in a streak of light known as a meteor. If the meteoroid does not burn up completely, what's left strikes Earth's surface and is called a meteorite.
Of all the meteorites examined, 92.8 percent are composed of silicate (stone), and 5.7 percent are composed of iron and nickel; the rest are a mixture of the three materials. Stony meteorites are the hardest to identify since they look very much like terrestrial rocks.
http://www.solarviews.com/eng/asteroid.htm
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