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    Monday, October 02, 2023

    Messenger to Mercury

    By the time this column runs, NASA’s Messenger spacecraft should have run out of fuel and slammed into the planet Mercury’s surface at around 9,000 miles per hour.

    The 9-foot probe is expected to leave a crater nearly five times its size, ending the 11-year mission with a bang on Thursday. Objects, both natural and man-made, often come to a violent end in space and this was exactly the plan.

    Messenger’s adventure encompassed 5 billion miles, including 15 trips around the sun, one flyby past Earth again, two around Venus, and three around Mercury before settling into a four-year orbit in 2011.

    Remember not so long ago when the only place we knew for sure water existed was Earth? Now, it seems, we find it everywhere we look in our solar system. (As a high-schooler with an online diary back in 1999, I thought I was being clever and ironic with the username Water on Mars. Now that moniker would earn me a "no kidding" reaction.)

    There is, indeed, water on Mars, and, as Messenger taught us, there’s also water on Mercury. It took many years and many billions of miles to acquire this information. Messenger was launched in 2004 and entered Mercury’s orbit on March 17, 2011. In its four-plus years orbiting the planet, Messenger collected more than a quarter-million images and other sets of data.

    The takeaway is that Mercury is far from just a stark, dead, torched rock. Data collected in 2012 showed a lot of ice on Mercury’s north and south poles. Some of the polar craters on its surface never see sunlight despite the planet’s close proximity to the sun. Turns out, ice was hiding there. So was a layer of “dark organic material” (dirt? meteor dust?) covering that ice, nestled with it in the craters’ recesses.

    The Messenger mission is viewed as a resounding success, considering scientists got three extra years of time with the probe than they had originally planned. After the craft goes out in a blaze of glory, the wealth of data it leaves for scientists to sift through should continue to tell us more about the solar system for years to come.


    Twitter: @o_starry_night


    4: Full moon.

    May 5-6: Eta Aquarids meteor shower. This is best viewed from the Southern Hemisphere, but in the Northern Hemisphere, up to 30 meteors per hour can zip across the sky. This shower is produced by dust particles left behind by the one and only Halley’s Comet. Light from the nearly full moon will unfortunately drown out all but the brightest meteors. Best viewing will be after midnight as far from any light pollution as you can get. Meteors will radiate from the constellation Aquarius, but can appear anywhere in the sky.

    May 7: Mercury will be at greatest eastern elongation of 21.2 degrees from the sun. This is the best time to view Mercury since it will be at its highest point above the horizon in the evening sky. Look for the planet low in the west just after sunset. (No dice on seeing the Messenger impact, though. That’ll happen on the side of Mercury facing away from Earth.)

    May 18: New moon.

    May 23: Up from some leisurely Saturn observing? The ringed one will be at opposition tonight, rendering it closer and brighter than at any other time of the year and visible all night long. A medium-sized or larger telescope wil show Saturn’s rings and its four brightest moons.

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