Cosmic Collisions

Mother Nature surely likes to throw her weight around.

The resulting collisions can be deadly, as any fan of the dinosaurs can tell you, but they do have their silver linings.

If you think your cosmic collisions knowledge is smashing, put it to the test with this quiz!

by Irene Klotz

The entourage circling Saturn includes a large and diverse collection of moons. One was nearly bashed to bits by a meteor or asteroid impact.

The crater left behind is about 88 miles wide -- nearly one-third of the diameter of the moon itself! A crater with those proportions on Earth would stretch from Los Angeles to New York.

The lucky survivor is:

In 1984, a team of meteorite hunters in Antarctica found an odd potato-shaped rock weighing nearly 5 pounds. It was partly covered with black glass -- a telltale sign that it burned through Earth's atmosphere before crashing some 13,000 years ago.

When scientists analyzed the rock, traces of gas in it matched Mars' atmosphere and -- for the first time -- what appeared to be the fossilized remains of bacteria.

The object, known as ALH 84001 or the Allan Hills meteorite, was launched off Mars by:

The secret to what killed off the dinosaurs 65 million years ago is thought to lie beneath Mexico's Yucatan Peninsula.

It's a crater known as Chicxulub, that measures 112 miles in diameter and 3,000 feet deep -- the footprint of an asteroid impact so powerful that it changed Earth's environment.

The size of the offending projectile was:

As the Earth was pulling itself together some 4.5 billion years ago, an object about the size of Mars smashed into the planet, throwing up a cloud of material that would over time come together to form the moon.

That's the current theory of the moon's formation. A previous, seriously considered option was:

For the first time in history, scientists recently had a ringside seat to watch a comet crash into a planet. The comet had been discovered the previous year by astronomers Carolyn and Eugene Shoemaker and David Levy.

The impact sent plumes of material thousands of miles into space and caused dark scars on the planet.

The unlucky target planet was:

Closer to home, the most powerful meteorite impact in recent history occurred on June 30, 1908.

Scientists estimate that a 220-million-pound space rock entered Earth's atmosphere traveling about 33,500 mph. The entry ignited the atmosphere to temperatures as high as 44,500 degrees Fahrenheit as it fell through the sky.

When it was about 5 miles from the ground, heat and pressure burst the rock into pieces and triggered a massive fireball comparable the energy in about 185 Hiroshima bombs

The blast, known as the Tunguska explosion, took place over:

At the end of 2003, seven major solar storms caused highly charged particles to come crashing into Earth's magnetic field, triggering power outages in Sweden, damaging satellites and disturbing airline routes.

Solar storms aren't all bad news, however. They are also responsible for:

There's a big hole in the ground some 43 miles east of Flagstaff, Ariz., stretching about 4,000 feet in diameter and about 570 feet deep.

Known as Barringer Crater or Meteor Crater, it is one of the best-preserved -- and also one of the first -- craters to tied to a meteor impact.

Scientists think the force of the blast that carved out the crater to be:

The end of days may have a name: Apophis -- a massive asteroid that could be on a collision course with Earth.

Four years ago, NASA scientists announced that there was a 1 in 17 chance Apophis would smash into Earth in 2029. The estimate was later revised to 1 in 45,000, then lowered again last year to 1 in 450. Suffice it to say that keeping watch for potentially killer asteroids is a full-time occupation these days.

Engineers, meanwhile, have a few ideas about how to deflect an incoming asteroid, including:

Even though space is vast and expanding, gravitational forces put galaxies on collision courses.

The resulting crashes can annihilate some structures, but also generate fodder for new stars.

Even our own Milky Way galaxy is on a collision course, destined to one day crash into: