October 9, 2007 3:24 PM PDT
NASA scoops up planetary details on Jupiter flyby
New Horizons, a robotic probe that's due to arrive at Pluto by the summer of 2015, flew within 1.4 million miles of Jupiter at the end of February--collecting data, images and video on the planet and its four largest moons. The piano-size probe was routed to pass by Jupiter so it could gather enough speed from the planet's gravity to get to Pluto three years sooner, scientists said. Another happy side effect was the discovery of new details about the planet, which NASA released this week through the journal Science.
"The most exciting part of the mission was the fortuitous opportunity to see relatively rare events," said Jeff Moore, a research scientist at NASA Ames Research Center and chairman of the Jupiter Encounter Science Team.
Those events were largely a stroke of luck and timing.
For example, a month before the probe flyby, a meteorite struck the thin, charcoal rings that surround Jupiter, allowing the scientists to further study their structure and matter. (NASA was able to capture images of meteorite clumps floating in the Jovian rings.) Scientists haven't known much about the rings because of their orbital trajectories and darkness--Earth is about 1,000 times brighter than Jupiter--but they now understand a bit more about them.
"The rings are comprised of pebble- to boulder-size particles, which form ringlets as you approach Jupiter," said Moore. "But looking back on the rings you'll see a very fine dust around them."
Similarly, the New Horizons probe caught thunderstorms and huge lightning strikes in Jupiter's polar region. NASA had seen such weather in Jupiter's mid-latitudes before, but it had not known about them in polar regions. "Our data suggests that there are thunderheads the size of a Western state," Moore said.
When the probe passed by, it also was able to capture data on a super-volcano eruption on Io, one of Jupiter's four large moons and which is only slightly larger than the Earth's moon. New Horizons captured Io spewing lava from the volcano Tvashtar 200 miles into space. It also measured lava temperatures up to 1,900 degrees Fahrenheit, similar to many terrestrial volcanoes.
Finally, New Horizons was the first robotic craft to get close enough to further study the rare formation of a small red spot on Jupiter. Most people know about Jupiter's Great Red Spot, a high-pressure cloud formation that's roughly three times the size of Earth's diameter. (In comparison, the Little Red Spot equals about 70 percent of Earth's diameter, but sits at a different latitude.) By collecting data and images to study the structure and motion of the Little Red Spot, NASA scientists have come up with a hypothesis for how the clouds are formed.
NASA's Moore said that Jupiter's atmosphere is composed of little white ovals that coalesce to form larger white ovals. Gases like sulfur atoms circulate through and off these ovals. But when an oval reaches a certain critical size, it forms a stagnant zone, in which it's possible for sulfur compounds to change the color from white to yellow to red, he said.
"We didn't understand that process until we saw a white oval turn red," he said.
Launched in January 2006, New Horizons' mission is to collect data about the never-before-seen Pluto. It's the fastest spacecraft NASA has ever launched, and it's now halfway between the orbits of Jupiter and Saturn, or more than 743 million miles from Earth. The probe has seven sensors and cameras that have recorded 700 events in the Jovian system, twice the activity planned for Pluto. The vehicle will not return to Earth, but will likely leave our solar system within a hundred years.
"Not only did (Jupiter) prove our spacecraft and put it on course to reach Pluto in 2015, it was a chance for us to...return important data that adds tremendously to our understanding of the solar system's largest planet and its moons, rings and atmosphere," New Horizons Principal Investigator Alan Stern said in a statement.
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