WASHINGTON – NASA scientists are looking at Mercury anew and are surprised at what they're seeing.
After decades of waiting to return to the planet after three fly-bys in 1974,they are finally getting their chance to study the closest planet to the sun.
Scientists gathered at NASA headquarters Wednesday to discuss the Messenger mission,the first mission to Mercury since Mariner 10, which was launched in 1973 and also visited Venus. After Mariner 10,however,55 percent of Mercury remained unseen. Of that,the scientists said they've now viewed another 30 percent.
Launched in 2004,Messenger traveled more than 2.2 billion miles,passed Mercury at an altitude of 124 miles and captured images of the never-seen side of Mercury,.
“It was not the planet we expected. It was not the moon,” said Sean Solomon,the mission's principle investigator.
Although the photographs NASA released seem to resemble the moon,scientist Robert Strom,a member of the Messenger science team who also worked on Mariner 10, explained how Mercury is not similar to the moon. The new data also differs from that gathered by Mariner 10.
“Every part of the planet,seen or unseen,is new,” Strom said.
By looking at craters on Mercury,Strom said it is apparent that gravity is stronger there than on the moon. Information about craters can be crucial to understanding the geologic history of the planet. It also aids scientists in developing a theory of the formation of Earth.
Mercury's craters have a different chemical make-up than those on the moon,making them look light on the inside. Volcanic activity may be the cause. The moon's craters appear dark on the inside. Scarps,raised patterns or ridges,also appear all over Mercury,including a spoke-like pattern centered in one crater.
The mission's primary goal is to study Mercury's atmosphere and chemical composition. Messenger arrived at its closest point in the early morning hours of Jan. 14 and took 1,213 images.
Since then,scientists at NASA have been studying data from the unmanned craft's seven instruments that measure the planet's topography and make-up.
Messenger's instruments are designed for use in the extreme environment near the sun – the temperature can range from 840 degrees to minus 275. The Mercury Dual Imaging System has two cameras. A wide-angle,color camera has 11 filters that help scientists determine what types of rocks are on the planet's surface. The narrow-angle camera can take very detailed black and white images.
Also on board is the Mercury Laser Altimeter,a device that uses an infrared laser transmitter to map the planet's surface. Data provided by the MLA show that the highest peak on the planet is about 3.1 miles above the surface level,and the lowest basin falls nearly 2 miles.
The exploration is also giving insight into the planet's magnetosphere,the protective “bubble” around a planet that can change due to solar wind and radiation exposure. Mercury is the only other example in our solar system of an Earth-like magnetosphere. Sean Solomon,principle investigator for the mission,said scientists will continue to research the ever-changing composition of that magnetosphere.
This project has been a long time in the making.
“If you can imagine,I was very excited about this mission,” Strom said. “Particularly on the eve of the encounter I couldn't sleep at all. I was like a kid on Christmas Eve. But,unlike that kid on Christmas Eve,I'd waited 30 years for this.”
Messenger is scheduled to make two more close passes to the planet,in October and in September 2009.
“Making discoveries is the biggest turn-on in the entire universe. Believe me,it is,and this is what this mission is about – discoveries. That's one of the reasons I'm so excited about it,” Strom said.