October 22, 2017

28.9.9: Messenger’s 3rd Flyby of the Planet Mercury.

The drama in the inner solar system continues… late tomorrow on September 29th, NASA’s Messenger space probe will do its third and final swing by of the planet Mercury. At closest approach, Messenger will be less than 142 miles above the surface and provide more stunning images of the inner world. Wide field UV spectroscopy scans should begin later today, and this gravity assist will be the final pass for eventual orbital insertion around Mercury in 2011. About 90% of Mercury has been mapped, although Messenger is only the second spacecraft to examine Mercury up close after Mariner 10 in 1974…did you know that Mariner 10 created a brief buzz of excitement when it appeared to have discovered a “moon” of Mercury? The anomalous UV radiation was later accounted for by the star 31 Crateris, but it serves as a reminder that we don’t know everything about this tiny world. I also mention this because in the days after its pass, Messenger will conduct a wide angle satellite search as it calibrates its cameras… such a discovery would be just plain cool! Messenger has been busying itself by conducting a survey for any hypothetical “Vulcanoids” interior to Mercury’s orbit, and will conduct measurements with its Laser Altimeter tomorrow during its closest pass. Mercury is currently low in the dawn sky, rising about an hour before the Sun. A very cool time-line is provided for those who want to follow the action!