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Ever since the violent beginning of our solar system planets, moons, comets and asteroids have collided with each other leaving behind evidence in the form of craters. By observing the surface of our moon we can see back through time and see the destructive and natural history of the solar system. The newly formed crater on Juno shows that this planetary process is still in operation.
Juno was the third asteroid to be discovered by astronomers early in the 19th century. It orbits the Sun with thousands of other bits of space rock in the main asteroid belt between Mars and Jupiter. One of the largest asteroids at over 240 kilometres in diameter. Even at this size Juno offers very little to look at with the naked-eye, trying to see Juno would be equivalent to spotting a penny from 11 kilometres away. To study the surface astronomers needed to combine various new technologies.
To solve the problem scientists combined an adaptive optics system with the almost 100 year old Hooker telescope at the Mount Wilson Observatory, Pasadena, USA. An adaptive optics enables compensation for the distortion created by our planet's atmosphere allowing the images to be as sharp and clear as those taken in space. Using this technology a detailed map of Juno’ s surface was made.
The surface maps showed that Juno, like other asteroids, is an irregular, sharp-edged object. The images also revealed a large ‘bite’ taken from one side of the asteroid, a new crater almost 100 kilometres wide. The collision that caused this feature is expected to have occurred in the recent history, astronomical history that is.
The new impact crater will offer the scientists a window inside the asteroid with a convenient way to study an asteroids regolith and help see rare excavated material from beneath the surface. The blast would have thrown fragments out into space that could have sent samples to Earth.
The innovative use of combining technologies has given old historical observations a new lease of life, enabling Earth-based observations to be as clear as a space bound instruments. Now years after Edwin Hubble discovered evidence of the expanding universe with the Hooker Telescope, the telescope can continue to make groundbreaking discoveries today.
More info: Harvard-Smithsonian Center for Astrophysics
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