Jan 15 2008
A University of Michigan space instrument will take the first direct measurements of the planet Mercury's wispy atmosphere and space environment on Jan. 14, when NASA's MESSENGER spacecraft does its initial flyby of the closest world to the sun.
No spacecraft has visited Mercury since the Mariner 10 in 1975 mapped parts of the planet. This is the first of three flybys scheduled for the next two years, which will bring MESSENGER progressively closer to Mercury until it can enter orbit in 2011.
The Fast Imaging Plasma Spectrometer (FIPS) instrument onboard MESSENGER, designed and built at U-M, will take measurements to determine what Mercury's atmosphere is composed of and how the planet interacts with the space environment. The planet's magnetic field and its proximity to the sun provide an interesting test-case for interaction of the solar wind with terrestrial planets.
"Mercury's space environment is at the extreme," said Thomas Zurbuchen, FIPS instrument project leader and a professor in the department of Atmospheric, Oceanic and Space Science. "It's Earth-like because it does have a magnetosphere, but the planet is in the most violent part of the solar system. Radiation from the sun in the form of heat and particle radiation from the solar wind can rain down on Mercury."
On average, Mercury is just 36 million miles from the sun---about two-thirds closer than the Earth. And Mercury is the smallest planet in the solar system at just 3,000 miles across at its equator.
Like the Earth, Mercury has a magnetosphere---a field generate by the planet's iron core. On Earth, the magnetosphere protects us from the sun's heat and other forms of radiation including the charged particles in the solar wind. FIPS will help scientists figure out how Mercury's magnetosphere works.
Scientists believe Mercury's exceedingly thin atmosphere includes sodium, oxygen and potassium. Zurbuchen believes there's more too it.
"The vast majority of the components of Mercury's atmosphere, we have no clue about," he said.