About 7:50 a.m. Tuesday, NASA’s New Horizons spacecraft made its
closest pass by Pluto, coming within 7,800 miles of the surface. The craft’s
journey at a speed of 13,000 mph started 9 years ago and has traveled approximately 3 billion miles of space.
New Horizons' flyby of Pluto is a key
moment in the history of space exploration as it brings to completion the endeavor that started more than 50 years ago and continuing to today. It marks the fact that all planets in our solar
system have been visited.
Preliminary images and instrument
readings have revealed an icy sphere—about two-thirds the size of Earth’s moon.
Pluto is 2,370 kilometers across, making it the biggest known object beyond the
orbit of Neptune.
Its surface is marked by chasms and
craters and an enigmatic heart-shaped region. The dwarf planet has a
polar ice cap composed of frozen methane and nitrogen.
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