An asteroid is a minor planet of the inner Solar System. Sizes and shapes of asteroids vary significantly, ranging from 1-meter rocks to a dwarf planet almost 1000 km in diameter; they are rocky, metallic or icy bodies with no atmosphere.

Of the roughly one million known asteroids the greatest number are located between the orbits of Mars and Jupiter, approximately 2 to 4 AU from the Sun, in the main asteroid belt. Asteroids are generally classified to be of three types: C-type, M-type, and S-type. These were named after and are generally identified with carbonaceous, metallic, and silicaceous compositions, respectively. The size of asteroids varies greatly; the largest, Ceres, is almost 1000 km across and qualifies as a dwarf planet. The total mass of all the asteroids combined is only 3% that of Earth's Moon. The majority of main belt asteroids follow slightly elliptical, stable orbits, revolving in the same direction as the Earth and taking from three to six years to complete a full circuit of the Sun.

Asteroids have been historically observed from Earth; the Galileo spacecraft provided the first close observation of an asteroid. Several dedicated missions to asteroids were subsequently launched by NASA and JAXA, with plans for other missions in progress. NASA's NEAR Shoemaker studied Eros, and Dawn observed Vesta and Ceres. JAXA's missions Hayabusa and Hayabusa2 studied and returned samples of Itokawa and Ryugu, respectively. OSIRIS-REx studied Bennu, collecting a sample in 2020 to be delivered back to Earth in 2023. Lucy, launched in 2021, has an itinerary including eight different asteroids, one from the main belt and seven Jupiter trojans. Psyche, to be launched in 2023 or 2024, will study a metallic asteroid of the same name.

Near-Earth asteroids can threaten all life on the planet; an asteroid impact event resulted in the Cretaceous–Paleogene extinction. Different asteroid deflection strategies have been proposed; the Double Asteroid Redirection Test spacecraft, or DART, was launched in 2021 and intentionally impacted Dimorphos in September 2022, successfully altering its orbit by crashing into it.

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Nasa's Dart spacecraft 'changed path of asteroid'

The American space agency says its recent attempt to deflect the path of an asteroid was successful. Scientists have now confirmed the orbit of a 160m-wide (520ft) space rock known as Dimorphos was altered when the Dart probe struck it head on last month.

Asteroid struck by Nasa probe leaves 10,000km trail

BBC NewsA new image shows that an asteroid which was deliberately struck by Nasa's Dart probe has left a trail of debris stretching thousands of kilometres. A telescope in Chile captured the remarkable image of a comet-like plume spreading behind the giant rock.

Dimorphos: Nasa flies spacecraft into asteroid in direct hit

To play this video you need to enable JavaScript in your browser.By Jonathan AmosBBC Science Correspondent@BBCAmosThe American space agency's Dart probe has smashed into an asteroid, destroying itself in the process.

Nasa spacecraft lining up to smash into an asteroid

In the coming hours, the American space agency will crash a probe into an asteroid. Nasa's Dart mission wants to see how difficult it would be to stop a sizeable space rock from hitting Earth.

Impact crater may be dinosaur killer's baby cousin

When an asteroid slammed into what is now the Gulf of Mexico 66 million years ago, wiping out the dinosaurs, did it have a companion? Was Earth bombarded on that terrible day by more than one space rock?

Tanis: Fossil found of dinosaur killed in asteroid strike, scientists claim

To play this video you need to enable JavaScript in your browser.Scientists have presented a stunningly preserved leg of a dinosaur.The limb, complete with skin, is just one of a series of remarkable finds emerging from the Tanis fossil site in the US State of North Dakota.

Don't Look Up: What's the plan to deal with asteroids and comets?

It's understandable if the thought of a comet wiping out all life on earth might be an extra worry you just don't need right now. But if you've watched Netflix movie Don't Look Up, it might be hard to get the thought out of your mind.

Nasa Dart asteroid spacecraft: Mission to smash into Dimorphos space rock launches

Nasa's Dart mission wants to see how difficult it would be to stop a sizeable space rock from hitting Earth. The spacecraft will crash into an object called Dimorphos to see how much its speed and path can be altered.

Apophis asteroid will not hit Earth for 100 years, Nasa says

Earthlings can breathe a sigh of relief after US space agency Nasa confirmed the planet was "safe" from a once-feared asteroid for the next 100 years at least. Nasa had deemed Apophis to be one of the most dangerous asteroids to Earth after its discovery in 2004.

Asteroid that wiped out dinosaurs shaped fortunes of snakes

Snakes owe their success in part to the asteroid strike that wiped out the dinosaurs, according to a new study. The impact caused devastation, with most animals and plants dying out.

Dinosaur-killing asteroid strike gave rise to Amazon rainforest

The asteroid impact that killed off the dinosaurs gave birth to our planet's tropical rainforests, a study suggests. Researchers used fossil pollen and leaves from Colombia to investigate how the impact changed South American tropical forests.

Hayabusa-2: Pieces of an asteroid found inside space capsule

Scientists have been greeted by the sight of jet black chunks of rock and soil from an asteroid after opening a capsule that returned from deep space a week ago.

Hayabusa-2: Capsule with asteroid samples in 'perfect' shape

A capsule containing the first significant quantities of rock from an asteroid is in "perfect" shape, according to scientists.The container with material from a space rock called Ryugu parachuted down near Woomera in South Australia on Saturday evening (GMT).

Hayabusa-2: Rocks from an asteroid set for delivery to Earth

The first large sample of rock and soil from an asteroid is making its way back to Earth. The sample container should deploy parachutes and land in the Australian outback this evening.

Osiris-Rex: Nasa probe risks losing asteroid sample after door jams

image copyrightReutersA Nasa probe sent to collect rock from an asteroid several hundred million kilometres from Earth has grabbed so much that samples are spilling out.

Winchcombe meteorite bolsters Earth water theory

By Jonathan AmosBBC Science Correspondent@BBCAmosA meteorite that crashed on the Gloucestershire town of Winchcombe last year contained water that was a near-perfect match for that on Earth.

Somalia meteorite: Joy as scientists find two new elements

Image source, Supplied to University of AlbertaBBC NewsA huge meteorite that fell to Earth contains two minerals never seen before on our planet, scientists say.Canadian researchers said the rock was found in rural Somalia two years ago, but locals believe it is much older.

US detects huge meteor explosion

The blast was the second largest of its kind in 30 years, and the biggest since the fireball over Chelyabinsk in Russia six years ago. But it went largely unnoticed until now because it blew up over the Bering Sea, off Russia's Kamchatka Peninsula.

James Webb Space Telescope hit by tiny meteorite

The damage inflicted by the dust-sized micrometeoroid is producing a noticeable effect in the observatory's data but is not expected to limit the mission's overall performance. James Webb was launched in December to succeed the revolutionary - but now ageing - Hubble Space Telescope.

Christie's auction: Kennel hit by meteorite goes on sale

A chunk of Mars, some of the space rock that splattered a quiet English town and a dog kennel pierced by an object that came out of the sky.All three items go under the hammer on Wednesday when London auction house Christie's holds its annual sale of rare and unusual meteorites.

Large meteor wows Norway after blazing through night sky

Norwegians have been left awestruck by what experts say was an unusually large meteor that illuminated the night sky in the country's south-east. Footage shows powerful flashes of light over Norway, followed by what witnesses described as loud bangs on Sunday.

US meteorite adds to origins mystery

In January 2018, a falling meteorite created a bright fireball that arced over the outskirts of Detroit, Michigan, followed by loud sonic booms. The visitor not only dropped a slew of meteorites over the snow-covered ground, it also provided information about its extra-terrestrial source.

Astronomy Photographer of the Year: 'Once in a lifetime' picture of comet wins award

The image shows a piece of Comet Leonard's tail breaking off and being carried away by the solar wind. The comet made a brief appearance to Earth after being discovered in 2021, but has now left our Solar System.

Nasa scientists spy 'largest comet ever seen'

Nasa's Hubble telescope has determined the comet's icy nucleus has a mass of about 500 trillion tonnes and is 85 miles (137km) wide - larger than the US state of Rhode Island. But not to worry. The closest it will get is one billion miles away from the Sun, and that won't be until 2031.

C/2014 UN271 (Bernardinelli-Bernstein)

C/2014 UN271 (Bernardinelli-Bernstein), or simply 2014 UN271, is a large Oort cloud comet discovered by astronomers Pedro Bernardinelli and Gary Bernstein in archival images from the Dark Energy Survey.[6][7] When first imaged in October 2014, the object was 29 AU (4.

The mysteries of the icy cloud around our Solar System

For a few weeks in the summer of 2020, if you had been looking up on a clear night, there is a chance you might have spotted a rare visitor to our part of the Solar System.


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