Andrew Fazekas
for National Geographic News
Published June 4, 2010
Hot on the heels of last year's asteroid impact on Jupiter, the gas giant planet has been smacked once again.
In 2009 backyard astronomers saw a dark blemish on Jupiter that marked the spot where a space rock had slammed into the Jovian atmosphere.
This time, Anthony Wesley in Australia and Christopher Go in the Philippines both saw the actual moment of impact.
Photos and video show the bright flash as an Earth-size fireball rises above Jupiter's atmosphere on June 3 at 4:31 p.m. ET.
"The data—independently confirmed by two well-respected amateurs—seem robust, and the flare certainly bears all the characteristics of a Jovian 'bolide,' or impact," said Heidi Hammel of the Space Science Institute in Boulder, Colorado.
Race to See Jupiter's New Impact Scar
The recent impact happened the same day Hammel and her team released new photos and analysis of the 2009 Jupiter collision. According to the study, the previous impact was caused by a 1,640-foot-wide (500-meter-wide) asteroid.
Scientists are now racing to get professional and amateur astronomers to train their telescopes on the gas giant to see what kind of scar will be left behind by this latest impact and hopefully what kind of object hit the giant planet.
Experts believe the collision should produce a dark debris field in Jupiter's clouds—similar to the previous impact site—which may become visible over the next few days. (Related: "Jupiter Loses Big Belt; Great Spot Left Hanging.")
"We don't know if there is a dark site yet, since this appears be a small impact," Hammel said. "We are working on getting telescopes around the world in gear for followup work, including the world's largest telescopes and [the] Hubble" Space Telescope.
Second Jupiter Impact "Unbelievable"
Meanwhile, the odd coincidence of two Jovian smashes so close together has astronomers scratching their heads, since impacts on Jupiter have long been thought to be relatively rare.
Until the 2009 collision, the last known impact event on Jupiter was the famous "death" of Comet Shoemaker-Levy 9 in 1994.
"'Unbelievable' has been the word in many of the first emails about this one just seen," Hammel said. "It's back to the drawing board on our understanding of the statistics of impacting bodies."
A similar impact occurred last July after a large asteroid collided into the planet.
A large object, possibly an  or a , hit the planet Jupiter Thursday, resulting in a large fireball.

The fireball was seen on June 3 at 2031  by two independent amateur astronomers, Christopher Go in the Philippines and Anthony Wesley in Australia. Wesley, who posted the news onto an , is known for having also spotted last July's . Go caught Thursday's impact on video, which showed a fireball the size of Earth after the object hit. It could be the first time someone has recorded a meteor crashing into a planet.

This latest strike came only hours after a team from the , led by astronomer , announced that last year's event was the result of an asteroid 1,640 feet (500 metres) wide. That asteroid caused a scar the size of the  when it hit Jupiter with the force of several thousand nuclear bombs on July 19, 2009.

The planet last experienced a major impact in July 1994, when it was hit by  (SL9), resulting in large scars as well. Scientists originally thought that there would not be any more Jupiter strikes for several centuries following SL9, but have now been proved wrong twice in as many years.

Now, astronomers around the world are trying to figure out what kind of mark Thursday's collision left on the planet, as well as determine exactly what hit it. Although the impact is believed to be relatively small, a dark debris field may soon appear in the clouds around Jupiter, which is what occurred in 2009.