June 3, 2020

17.03.11- Mercury: At Last!

Tonight marks a pivotal moment in solar system exploration. At 12:45 AM UTC on March 18th, NASAís Mercury Messenger spacecraft will burn its engines for approximately 15 minutes to enter an elliptical orbit around the planet Mercury. Since its launch from Cape Canaveral on August 3rd, 2004, Messenger has flown by the Earth once and Venus twice for a gravitational assist, swung by the innermost world three times, sampled the near solar environment, searched for Vulcanoids, and even done a wide field pan for any tiny Mercury moonlets that may have been missed.

The planet Mercury has been subject to brief flybys since the first and only one conducted by Mariner 10 in 1974, but never played host to a dedicated orbiter until today. †In fact, the entire surface of Mercury hadnít been accurately mapped until the advent of Messenger. A low cost ($446 million) Discovery class mission, Messenger sports a science payload including the Mercury Dual Imaging System (MDIS) Spectrometers designed to measure the x-ray, neutron, and gamma-ray environment, as well as various plasma and particle monitoring devices. Already, Messenger has detected an elusive anti-sunward ion tail related to the planet, and returned some stunning images from previous flybys. †A live webcast on the event is planned for tonight at 7:55 PM EDT/11:55 PM UT, but donít expect pretty pictures to become routine until a few weeks post insertion. March 23rd will mark the start of a complete wring through of the instrumentation, and April 4th the true science phase of the mission begins.

Some of the questions that scientists hope to answer about Mercury are: why is it so dense? What is the history of this rocky world? How dynamic is its environment? This is planetary science in the making, as we hunker down to begin a proper survey of a new world. Messengerís primary mission is to orbit Mercury for one Earth year or just over four solar orbits of Mercury. And donít forget to look westward in the dusk skies tonight for Mercury low†to the horizon, and realize that a little unknown slice of the universe is about to become just a little more known!

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