NASA spacecraft orbiting around Mars continue to send data to Earth of the Siding Spring comet that whizzed past the Red Planet at 125,000 mph on Sunday.
NASA's three orbiters — the Mars Reconnaissance Orbiter, Mars Odyssey, and Mars Atmosphere and Volatile EvolutioN (MAVEN) — are transmitting data to NASA scientists, including an image of the comet's nucleus. Scientists are surprised by the size, which is half of what they were expecting.
The Siding Spring comet came from the distant Oort cloud, and was formed billions of years ago. The Los Angeles Times explains that the comet is "essentially a flying frozen time capsule from the solar system's earliest days," and is formed of water, gas, and dust. Scientists at first were afraid the comet could damage an instrument by cracking a camera or damaging an electrical system, but they knew they couldn't pass up their chance to see the comet up close. To avoid an accident, the orbiters were sent to the other side of the planet during the most dangerous time of the comet's fly by.
All three orbiters are still watching the comet, which is headed toward the sun, and NASA expects to keep collecting data for several more days.