NASA Messenger Probe Becomes First Spacecraft to Orbit Mercury

March 21, 2011 – Kristen Metz

NASA’s Messenger probe made history on the night of March 17, 2011, when it became the first spacecraft to successfully enter into Mercury’s orbit. Now, for the first time in history, Mercury has an artificial satellite. The spacecraft has been sent to study the closest planet to the sun in the hopes of studying the planet’s composition and magnetic environment. The Messenger will spend one Earth year studying Mercury and is a part of the first mission to study Mercury since the Mariner mission more than thirty years ago.

The Messenger spacecraft, which stands for Mercury Surface, Space Environment, Geochemistry, and Ranging, was launched in August 2004 at a cost of $446 million. Here are some facts about the spacecraft currently studying Mercury:

  • Since its launch 6 ½ years ago, the Messenger has traveled approximately 4.9 billion miles and has completed 15 orbits of the sun
  • Messenger’s average speed is 84,500 mph and has broken the record for all-time fastest spacecraft at a pace of 140,000 mph
  • The aircraft weights 2,420 pounds but is only 4.7 feet tall by 6.1 feet wide by 4.2 feet deep. Two solar panel “wings” measuring 5 by 5.5 feet are on either side of the probe.

Mercury has long remained a mystery to scientists. Until the Messenger flew by Mercury for the first time in 2008, only half of the planet had ever been seen. Scientists were finally able to see close-up pictures of the other half of Mercury’s surface. Here are some more facts about the planet Messenger has been sent to study:

  • Mercury is 35,980,000 million miles from the sun
  • Mercury’s year lasts for 88 days
  • The average daytime temperature is 800 degrees Fahrenheit, while the average nighttime temperature is -300 degrees Fahrenheit
  • The planet is named after Mercury, the Roman messenger of the gods

Now that Messenger is safely in orbit, the spacecraft will soon begin observations of the planet’s surface, atmosphere, and magnetic field. Below is a look at the scientific instruments Messenger is outfitted with that will help the spacecraft provide scientists with a never before seen look at the closest planet to the sun.
Studying the Surface

The spacecraft is outfitted with seven scientifically advanced instruments, three of which are specifically for studying the surface. In order to create a map of the planet’s landscape, the Mercury Dual Imaging System will utilize two cameras, one wide-angle and one narrow-angle. Also helping to create maps is the Mercury Laser Altimeter. The MLA uses a laser to reflect off of the surface of Mercury, which then gathers light through a sensor. This enables scientists to track the variation in the distance between Messenger and the surface of Mercury.

Mercury’s Crust

Several instruments have been implemented to study Mercury’s crust. Using a process known as spectroscopy, the instruments will relay information to scientists about the presence of rocks and minerals around Mercury. The X-ray Spectrometer (XRS) will detect X-rays that are emitted from Mercury’s crust via certain elements. Another instrument known as the Gamma Ray and Neutron Spectrometer (GRNS) works similarly by detecting gamma rays and neutrons from certain elements. The GRNS will also be helpful in determining if water ice exists in craters at Mercury’s poles.

Understanding Mercury’s Atmosphere and Magnetic Field

Messenger is equipped with the Mercury Atmospheric and Surface Composition Spectrometer (MASCS) to study the gases in Mercury’s atmosphere. The MASCS will also be able to help detect minerals on the surface of the planet. The magnetic field of Mercury will also be studied using Messenger’s Energetic Particle and Plasma Spectrometer (EPPS). The EPPS will study Mercury’s magnetosphere by measuring the electrons and ions present in the magnetic field, including their energy, layout, and composition.

Messenger’s Velocity

As Messenger orbits Mercury, it becomes attracted to areas with great mass where gravity pulls harder. This causes the spacecraft to speed up as it approaches and to slow down as it recedes. The Radio Science Experiment will use the Doppler Effect to track Messenger’s velocity. This will help the spacecraft determine how the planet’s mass is distributed, as well as the changes in the thickness of the planet’s crust.

What Comes Next

Now that Messenger has safely entered Mercury’s orbit, scientists from NASA and the John Hopkins University Applied Physics Laboratory will check the systems of the spacecraft and start turning on the instruments. Observations of the planet will begin on April 4th. After spending one Earth year observing the atmosphere, surface, and magnetic field of Mercury, Messenger will plummet back to Earth, but not before providing scientists with new information about the mysterious planet Mercury.

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