All large asteroids have been bombarded over the ages, and as a result smaller chunks have been cast adrift in the solar system. Some of these smaller bits fall to Earth as meteorites. One of the things we notice about meteorites is that many of them have certain similarities of composition and chemical signature. As a result they can be identified into groups. This would imply that these groups have a common origin, likely a particular asteroid.
Ancient Seas
Earth’s water is more ancient than you might suspect.
On the Rocks
We generally think of comets and asteroids as two distinct types of bodies. Comets are “dirty snowballs” of mostly ice, which vaporizes to form long tails when they approach the Sun, while asteroids are dry, rocky bodies that typically live in the asteroid belt. It is generally true that comets tend to have an icy surface of volatiles that can evaporate off its surface, and asteroids generally don’t. But it also turns out that the two are far more similar than they are different.
3 2 1 Contact
The Rosetta spacecraft is on its way to an asteroid known as 67P/Churyumov–Gerasimenko. In August it will go into orbit around the asteroid, and then in November it will put a lander known as Philae on the rock. The surface gravity of this asteroid is less than 1/20 that of Earth, so Philae will actually have harpoons to keep it attached to the asteroid. It’s an ambitious mission, since unlike many landings we have no idea what the surface of the asteroid will be like. In fact until recently, we weren’t entirely sure what the shape of 67P/Churyumov–Gerasimenko actually is.
Splat
The mass of the Moon is about 1% that of Earth. That might seem pretty small, but it’s actually surprisingly large. The moons of other planets are tiny when compared to their planet’s mass. Just how Earth got such a large moon has been a bit of a mystery, but it has generally come down to two models: co-formation and collision.
Color Kin
We generally think of asteroids as looking like gray rocks. While that’s true to our limited eyes, more sensitive instruments find they have a variety of colors. You can see an example of this in the image above of the asteroid Vesta. This false color image was made by observing Vesta at various wavelengths in the visible and infrared spectrum. It shows that Vesta has variations in color too subtle for us to see with our eyes.
Data Rock
In modern astronomy, large catalogs of data are vital to our understanding of the universe. But just what does it take to create these large catalogs? Scott Manley has a great video of one example, discovering and cataloging the asteroids in our solar system. It tracks asteroid discoveries from 1980 to the present.
Hot Rocks
Asteroids come in a range of sizes, from hundreds of kilometers in diameter down to a meter wide and smaller. Determining just how many asteroids there are is a challenge, because the smaller an asteroid’s size, the more difficult it is to observe.
Put a Ring On It
Astronomers have found an asteroid with a ring system. While this is the first discovery of a ring system about an asteroid, such a thing isn’t entirely unexpected. But what’s particularly interesting is how they discovered these rings.