Ten interesting facts about asteroids

February 3, 2015 by Elizabeth Howell, Universe Today
Artist’s conception of asteroids and a gas giant planet. Credit: Harvard-Smithsonian Center for Astrophysics

At first glance, looking at a bunch of space rocks doesn't sound that exciting. Like, aren't they just a bunch of rubble? What use can they be in understanding the Solar System compared to looking at planets or moons?

Turns out that asteroids are key to figuring out how the Solar System came to be, and that they're more interesting than they appear at first glance. Below, we have 10 facts about asteroids that will make you reconsider that biased first impression.

Asteroids are leftovers of the early Solar System.

The leading theory about how our neighborhood came to be is this: the Sun coalesced from a compressed grouping of gas that eventually began fusing atoms and creating a protostar. Meanwhile, the dust and debris nearby the Sun began to coalesce. Small grains became small rocks, which crashed into each other to form bigger ones. The survivors of this chaotic period are the planets and the moons that we see today … as well as a few smaller bodies. By studying asteroids, for example, we get a sense of what the Solar System used to look like billions of years ago.

Most asteroids are in a "belt."

While there are asteroids all over the Solar System, there's a huge collection of them between the orbits of Mars and Jupiter. Some astronomers think that could have formed into a planet if Jupiter was not nearby. By the way, this "belt" may erroneously create the impression that it is chock full of asteroids and require some fancy Millennium Falcon-style maneuvering, but in reality there are usually hundreds or thousands of miles in between individual asteroids. This shows the Solar System is a big place.

Asteroids are made of different things.

In general, an asteroid's composition is determined by how close it is to the Sun. Our nearby star's pressure and heat tends to melt ice that is close by and to blow out elements that are lighter. There are many kinds of asteroids, but these are the three main types, according to NASA:

10 interesting facts about asteroids
This image shows the Themis Main Belt which sits between Mars and Jupiter. Asteroid 24 Themis, one of the largest Main Belt asteroids, was examined by University of Tennessee scientist, Josh Emery, who found water ice and organic material on the asteroid’s surface. His findings were published in the April 2010 issue of Nature. Credit: Josh Emery/University of Tennessee, Knoxville
  • Dark C (carbonaceous) asteroids, which make up most asteroids and are in the outer belt. They're believed to be close to the Sun's composition, with little hydrogen or helium or other "volatile" elements.
  • Bright S (silicaceous) asteroids and are in the inner belt. They tend to be metallic iron with some silicates of iron and magnesium.
  • Bright M (metallic) asteroids. They sit in the middle of the and are mostly made up of metallic iron.

Asteroids also lurk near planets.

NASA also has classifications for this asteroid type. Trojans stay in the same orbit as a planet, but they "hover" in a special spot known as a Lagrangian point that balances the pull of the planet's gravity and the pull of the Sun. Trojans near Mars, Jupiter and Neptune have been discovered—as well as at least one near Earth in 2011. We also have near-Earth asteroids, which cross our orbit and could (statistically speaking) one day pose a threat to our planet. That said, no one has yet identified any one asteroid that will one day collide with our planet for sure.

Asteroids have moons.

While we think of moons as something that orbits a planet, asteroids also have smaller bodies that orbit them! The first known one was Dactyl, which was discovered in 1993 to be orbiting a larger asteroid called Ida. More than 150 asteroids are known to have moons, with more being discovered periodically. A more recent example is one discovered orbiting Asteroid 2004 BL86, which passed 750,000 miles (1.2 million kilometers) from Earth in early 2015.

Another set of images of 2004 BL86 and its moon. Credit: NAIC Observatory / Arecibo Observatory

We have flown by, orbited and even landed on asteroids.

Illustration of small asteroids passing near Earth. Credit: ESA / P. Carril

NASA says there are more than 10 spacecraft that accomplished at least one of these, so we'll just cover a couple of examples here. NEAR Shoemaker touched down and survived for weeks on 433 Eros in 2001 despite not being designed to do it. NASA's Dawn spacecraft spent months orbiting Vesta—the second-largest member of the asteroid belt—in 2011 and 2012. And in 2010, Japan's Hayabusa spacecraft made an astonishing return to Earth bearing samples of asteroid Itokawa that it nabbed in 2005.

Asteroids are too small to support life as we know it.

That's because they're too tiny to even hold on to atmospheres. Their gravity is too weak to pull their shape into a circle, so they're irregularly shaped. To get a sense of just how small they are in aggregate, NASA says the mass of all the asteroids in the Solar System is less than our Moon—which only has a tenuous "exosphere" itself.

Despite their small size, water may flow on . Observations of Vesta released in 2015 show gullies that may have been carved by water. The theory is that when a smaller asteroid slams into a bigger one, the small asteroid releases a layer of ice in the bigger asteroid it hit. The force of the impact briefly turned the ice into water, which streaked across the surface. (As for how the ice got there in the first place, it's possible that comets deposited it in some way—but that's still being investigated as well.)

An asteroid could have killed the dinosaurs.

The fossil record for dinosaurs and other creatures of their era show them rapidly disappearing around 65 million or 66 million years ago. According to National Geographic, there are two hypotheses for this event: an asteroid or comet hitting the Earth, or a huge volcano eruption. The case for an asteroid comes from a layer of iridium (a rare element on Earth, but not in meteorites) that is found all over the world, and a crater called Chicxulub in Mexico's Yucatan Peninsula that is about 65 million years old. Iridium, however, is also found inside the Earth, which lends credence to some theories that it was volcanoes instead. In either case, the resulting debris blocked the Sun and eventually starved those survivors of the impact.

At least one asteroid has rings. Called Chariklo, scientists made the surprise discovery in 2013 when they watched it pass in front of a star. The asteroid made the background star "blink" a few times, which led to the discovery that two rings are surrounding the .

Explore further: Scientists study surface composition of asteroid 2004 BL86 during close flyby of Earth

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cantdrive85
1 / 5 (2) Feb 03, 2015
Below, we have 10 facts about asteroids that will make you reconsider that biased first impression.
Speaking of biased opinions, most of their "facts" are anything but that. Let's review.

1.) Asteroids are leftovers of the early Solar System.

This is far from factual, it is merely an assumption based upon a belief system. No test can be devised to "prove" this as being a fact. Fail!

2.) Most asteroids are in a "belt."

This is likely true, it also suggests a common origin for this "belt". Note the belts proximity to the "God of War", Mars. The Jupiter comment is more nonsense though.

3.) Asteroids are made of different things.

Obvious, but the likelihood of it's positioning is due to the objects interaction with the Sun's electric field and not the Sun's "pressure".

4.) Asteroids also lurk near planets.

Also true, this begs the question as to why. Probably because that is where the asteroids originated.
cantdrive85
1 / 5 (2) Feb 03, 2015
5.) Asteroids have moons.

In respect to Pluto, we should call them dwarf moons.

6.) We have flown by, orbited and even landed on asteroids.

No obfuscation here, although I'm sure there are some conspiracy theories out there.

7.) Asteroids are too small to support life as we know it.

This is a fact, doesn't stop silly theories such as panspermia from being proposed though.

8.) An asteroid could have killed the dinosaurs.

This is more speculation. And since when did a fact involve "could have"?

9.) At least one asteroid has rings.

This begs the question as to how this can happen. Kristian Birkeland was able to replicate a ringed system in his lab experiments, it involved charged bodies in a plasma. You'd think this might be a hint, astrophysicists refuse to acknowledge this real fact however.

10.) This silly author from 'Universe Today' cannot count to ten, but since when has 'Universe Today' been concerned with "facts".

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