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NASA

NEAR FLyby of Asteroid Mathilde
News story originally written on July 3, 1997

On June 27, 1997, the NEAR spacecraft passed within 1200 km of the asteroid Mathilde. NEAR stands for Near Earth Asteroid Rendevous. It is one of NASA's Discovery missions, a series of small-scale spacecraft which are designed in less than three years and cost less than $150 million each.

Mathilde is a large asteroid. Its diameter was estimated to be 60 km and its mass was estimated to be 1x1017 kg. This makes it the most massive asteroid yet to be visited by a spacecraft.

Mathilde is also unique because it has an extremely long period of rotation. In fact, scientists have said that it hardly moves! It takes 17.5 days for Mathilde to rotate just once on its own axis.

This asteroid is located in the Main Asteroid Belt. It is assumed that asteroids in the Main Asteroid Belt date from the beginning of the solar system. Mathilde's dark surface (reflectivity is less than 4%) is believed to consist of carbon-rich materials that have not been altered by planet-building processes. Understanding asteroids such as Mathilde will point towards the solar system's origin.

The NEAR spacecraft has found five craters over 20 km across on the surface of Mathilde. No satellites (moons) have been found yet. And no evidence of water has been detected.

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