October 23, 2017

04.03.10: A Close Flyby of Phobos.

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Phobos on a pass of Mars Express last July. (Credit: ESA/DLR/FU Berlin/G. Neukum).

  

 The European Space Agencies’ (ESA) Mars Express orbiter completed the closest ever flyby of the misshapen Martian moon, Phobos, but don’t expect to see any mind blowing pictures…yet. Part of a series of 12 flybys, last nights’ pass skimmed to worldlet by 67 km, allowing its feeble gravity to deflect the space probe by a tiny but perceptible amount. This will allow engineers on the ground to get an idea of the internal density and composition of Phobos. But to do so, all instruments must be silent, so scientists can isolate minute oscillations on the probes carrier signal via the Doppler Effect. But take heart; Mars Express will further probe the moon on future passes via its MARIS radar, and will have its cameras switched on during next weeks’ March 7th pass…expect more cool pics soon!

10.10.09: An Active Mercury?

An atmosphere. Magnetosphere. Signs of recent geological activity…is it Mars? Europa? Some far off exo-planet? Nope…its none other than Mercury, a visual twin of our own Moon and long thought of as just as inactive. The past three flybys of NASA’s Messenger spacecraft have revealed a world of dynamic activity. First, there is Mercury’s on-again, off-again magnetic field, a sign that it may possess an active core. Now that 95%+ of the surface has been visualized, a picture is emerging of a crater pocked surface that has also been shaped by recent volcanism. Finally, Messenger has picked up tenuous traces of magnesium out-gassing from the planet as a result of the intense solar radiation bombarding the sun-ward side, contributing to a tenuous trailing exosphere. The 3rd pass last week was the closest yet, and revealed more stunning photos of what is now the tiniest “planet…” Messenger will enter a permanent orbit in 2011. Google Mercury, anyone?

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!