NASA Launches MESSENGER Spacecraft to Explore Mercury
Posted on: Wednesday, 4 August 2004, 06:00 CDT
NASA launches MESSENGER spacecraft to explore Mercury
WASHINGTON, Aug. 3 (Xinhua) -- NASA successfully launched its MESSENGER spacecraft early Tuesday, the first mission of this kind in 30 years to explore Mercury, the least-explored and closest planet to the Sun.
The MESSENGER (MErcury Surface, Space ENvironment, GEochemistry and Ranging) spacecraft was launched as planned aboard a Boeing Delta II rocket at 2:16 a.m. EDT (0616 GMT) Tuesday from Cape Canaveral Air Force Station in Florida.
NASA on Monday postponed the launch of MESSENGER for at least 24 hours due to bad weather.
The 4.27-million-US-dollar mission to explore Mercury is the first since NASA's Mariner 10 took a close look at the heavy-metal planet in 1974 and 1975. MESSENGER will fly some 7.9 billion km in the space before it enters Mercury's orbit in March 2011.
Scientists believe the study of Mercury will help understand the origin and evolution of the inner terrestrial, or rocky, planets, which also include Venus, Earth and Mars.
But above all, scientists hope that MESSENGER will help determine the composition of Mercury's surface and find if there is ice on the hottest planet in the solar system.
Mercury is very unusual among the inner rocky planets. Slightly larger than the Earth's moon, the planet has the density similar to that of the Earth. Scientists believe at least two-thirds of it must be made up of iron.
In addition, Mercury is the one with the largest daily variations in surface temperature. The temperature difference between day and night on it is up to 600 degrees Celsius, with a daytime temperature around 450 degrees Celsius.
As the interiors of large craters at Mercury's poles are permanently shadowed and remain always cold, below minus 212 degrees Celsius, scientists believe ice may exist there.
Radar images taken before of the polar regions show that the large craters' interiors are highly reflective, which suggests a possible presence of ice.
Scientists also hope MESSENGER can help them know more about Mercury's geologic history and the structure of its core.
Before it finally enters Mercury's orbit in 2011, MESSENGER will have to fly 15 times around the Sun. During the seven-year journey in space, it will fly past the Earth once, Venus twice and Mercury itself three times. The planetary gravity will slow the spacecraft in each flyby.
It would take three months for MESSENGER to travel to Mercury, 91 million km away from Earth, by a direct route, NASA said. But this would demand more fuel for braking maneuvers, thus needing a bigger rocket and higher cost.
When it runs out of fuel in 2012 or 2013, MESSENGER is expected to crash onto Mercury's surface.
The craft, 1.2 tons in weight, carries seven scientific instruments. There are spectrometers for remote chemical analysis, an imaging system, magnetometers to study Mercury's magnetic field, and an altimeter to measure the planet's topography.
To resist the high heat from the Sun, MESSENGER has a ceramic- material, curved and rectangular screen which will always face the Sun.
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