Deep Impact: Jupiter Hit by Comet or Meteoroid

July 21, 2009 — -- If you live in the southern hemisphere of Jupiter, you probably had a rough day Sunday.

Something -- possibly a comet or meteoroid undetected by earthlings -- went slamming into the planet, was swallowed up in its thick atmosphere of ammonia and methane, and left the "scar" you see in the image opposite from NASA's Infrared Telescope Facility atop Mauna Kea in Hawaii.

It was first spotted by an amateur Australian astronomer, Anthony Wesley, who realized he was seeing something unusual, and reported it to NASA in the United States.

"I suspect the impact scar itself should remain visible for a few days, maybe a week," said Leigh Fletcher, a scientist at NASA's Jet Propulsion Laboratory in Pasadena, Calif., who monitored the aftermath of the impact.

The mark is roughly the size of Earth, Fletcher said. Having missed the actual impact, astrophysycists say they may never be able to know the size of the object that hit Jupiter.

"We were extremely lucky to be seeing Jupiter at exactly the right time, the right hour, the right side of Jupiter to witness the event. We couldn't have planned it better," said Glenn Orton of the Jet Propulsion Lab.

Jupiter will heal. In the 4.6 billion years since the solar system formed, its powerful gravity has drawn in a disproportionate share of the debris that wanders through space between planets. Since Jupiter is mostly a mix of thick gases, it will absorb this latest impact, much as a lake settles down after you toss a stone in the water.

Some scientists, including Donald Brownlee and Douglas Ward in their book "Rare Earth," argue that Jupiter's presence has done a lot to allow the rise and endurance of life on Earth.

Even though Jupiter is half a billion miles away, on average, its powerful gravity does Earth a favor. It diverts a fair amount of the random stuff -- comets, asteroids, meteoroids and the like -- that might otherwise have hit Earth.