By Kristen Davidson
A new messenger is in the heavens Monday morning, August 2, courtesy of NASA.
NASA sent a probe, called the Messenger, to orbit Mercury. It will be the second unmanned flight to take pictures of Mercury.
The probe will take nearly eight years to complete its mission of examining the closest planet to the sun.
Messenger Spokesman Michael Buckley said he is excited for this chance to view Mercury up close.
'It''s a fantastic mission, poised to answer a range of questions about Mercury that have puzzled scientists for more than 30 years and give us the closest look yet at one of our nearest planetary neighbors,' Buckley said.
Messenger will be the first probe to orbit Mercury and the second spacecraft to fly next to Mercury. A spacecraft called the Mariner 10 flew by the little planet only three times in 1974 and 1975. New pictures of Mercury are needed because while the pictures Mariner 10 took were a breakthrough at the time, they are below standard for today''s technologies.
The trip will take the probe six and a half years to reach Mercury because of the different phases it will have to go through in order to successfully join up with the planet.
'Flybys - one of Earth, two of Venus and three of Mercury - allow Messenger to match Mercury''s speed and location, putting it in position to go into orbit by firing its onboard rocket motor,' Buckley said. 'A direct trip to the planet without flybys would have required a much larger launch vehicle and more onboard fuel than was practical to carry.'
The gravity-assisted flybys will occur for Earth in August 2005, Venus in October 2006 and June 2007, and for Mercury in January 2008, October 2008 and September 2009. The Messenger probe will finally enter Mercury''s orbit in March 2011.
NASA teamed up with Johns Hopkins University and Carnegie Institute at Washington to help with the launch and mission.
According to the Johns Hopkins University Web site, many questions about Mercury have gone unanswered. Scientists know Mercury is the densest planet but don''t have any definite explanations why.
Mercury''s density is twice as much as Earth at 5.3 grams per cubic centimeter. There are three theories that attempt to explain this phenomenon. The first theory has to do with the idea that the cloud Mercury came from dense particles. The second idea is that the heat of the sun vaporized the outer layer of the planet leaving dense metals behind. The third theory suggests that after the planet was formed, giant impacts whittled away the top crust leaving the dense rock behind.
The Messenger spacecraft will determine which of these ideas is correct by measuring the composition of the surface. Pictures the probe will transfer back are also expected to help answer question. Messenger is an acronym that stands mercury surface, space environment, geochemistry and ranging.
Since the probe will undertake extremely hot temperatures as it approaches the sun, scientists have spent extensive time designing the probe to withstand the heat.
'Messenger''s first line of thermal defense is a heat-resistant and highly reflective sunshade, fixed on a titanium frame to the front of the spacecraft,' Buckley said. 'The thin shade has front and back layers of Nextel ceramic cloth, while temperatures on the front of the shade could reach 370 degrees C (698 degrees F) when Mercury is closest to the Sun, behind it the spacecraft will operate at room temperature, around 20 degrees C (68 degrees F).'
In addition to the reflective sunshade, the next heat defense is several multi-layered insulation 'blankets.' The third protective measure the probe has is the many radiators and one-way heat pipes installed all over the probe to lead the heat away from the body of the probe.
'The combination of the sunshade, thermal blanketing and heat-radiation system allows the spacecraft to operate without special high-temperature electronics,' Buckley said.
John Strom of Carnegie Institution at Washington said the cost of the entire mission is $427 million including the $286 million Messenger probe. Carnegie Institution at Washington and its Department of Terrestrial Magnetism are highly involved in the Messenger mission.
'Messenger will illuminate processes that affect all the terrestrial planets,' said Sean Solomon, a principle investigator from Carnegie Institution of Washington.
The first launch took place at Cape Canaveral Air Force Station in Florida at 2:16 a.m. EDT. There are 13 scheduled days for the launch period, from August 2 to August 14, each with a 12-second launch window. The launches will be shown on NASA TV and Web cast on NASA Direct.