MESSENGER to Enter Mercury's Orbit to Answer Questions about the Planet

Mercury mission coincides with journey of New Horizons as it crosses the orbit of Uranus

by Catherine McNiff

On August 3, 2004, the MErcury Surface, Space ENvironment, GEochemistry and Ranging (MESSENGER) spacecraft achieved successful liftoff, commencing an eight-year mission "to unravel the mysteries of planet Mercury." Along the way, its team of scientists is witnessing flybys of Earth, Venus, and Mercury before the craft settles into an Earth-year-long orbit of the "innermost" planet, beginning on March 18, 2011. During the orbit, the spacecraft will travel 22.7 million miles in a highly elliptical shape that will bring it as close as 125 miles to Mercury and will range as far as 9,400 miles away from it. The all-composite spacecraft is the first of its kind and is powered by two solar panels, with energy stored in a nickel-hydrogen battery. MESSENGER's payload consists of seven scientific instruments whose sole purpose is producing data to answer six important questions about Mercury:

• Why is Mercury so dense?
• What is the geologic history of Mercury?
• What is the nature of Mercury's magnetic field?
• What is the structure of Mercury's core?
• What are the unusual materials at Mercury's poles?
• What volatiles are important at Mercury?

By answering these questions, NASA scientists hope to better understand not only Mercury, but also the origins of our own planet.

New Horizons

The Pluto-seeking New Horizons spacecraft shares MESSENGER's date with destiny. March 18, 2011, will mark the moment that the "ambassador to the planetary frontier" crosses the orbit of Uranus on its way to the edge of our solar system. An unmanned spacecraft equipped with an array of scientific instruments will be on board to gather information to answer four nagging questions about Pluto:

• What is its atmosphere made of, and how does it behave?
• What does the surface of Pluto look like?
• Are there big geological structures?
• How do particles ejected from the sun (known as the solar wind) interact with Pluto's atmosphere?

According to the New Horizons mission plan, inception date 2006, the probe has left Mars, Jupiter, and Saturn in its planetary dust. Next the craft will cross the orbit of Neptune in Aug. 2014, and will enter the Pluto system with a dramatic flight past the icy planet and its moons in July 2015.

Planetary pointers:

• Mercury is named for the Roman god of commerce, travel, and thievery (Greek god Hermes); a logical choice for the fastest planet in the stratosphere.
• Pluto is named for the Roman god of the underworld (Greek god Hades), perhaps because the dwarf planet is so far away.
• Pluto was named by an 11-year-old English girl named Venetia Phair in 1930.

Source: NASA.gov

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