Starship Asterisk*

MESSENGER's Last Day on Mercury

Explanation: The first to orbit Mercury, the MESSENGER spacecraft came to rest on this region of Mercury's surface yesterday. Constructed from MESSENGER image and laser altimeter data, the scene looks north over the northeastern rim of the broad, lava filled Shakespeare basin. The large, 48 kilometer (30 mile) wide crater Janacek is near the upper left edge. Terrain height is color coded with red regions about 3 kilometers above blue ones. MESSENGER'S final orbit was predicted to end near the center, with the spacecraft impacting the surface at nearly 4 kilometers per second (over 8,700 miles per hour) and creating a new crater about 16 meters (52 feet) in diameter. The impact on the far side of Mercury was not observed by telescopes, but confirmed when no signal was detected from the spacecraft given time to emerge from behind the planet. Launched in 2004, the MErcury Surface, Space ENvironment, GEochemisty and Ranging spacecraft completed over 4,000 orbits after reaching the Solar System's innermost planet in 2011.

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Did it impact at 87,000 MPH or 8,700 MPH? Sources other than APOD have the speed at 8700 MPH.

cydcharisse wrote:Did it impact at 87,000 MPH or 8,700 MPH? Sources other than APOD have the speed at 8700 MPH.

The latter. You've found a mistake. I'll email the editors.

Try to imagine, if you will, how all this appears to a person who was a teenager when the word came out in October 1957 that the Russians had put a satellite into orbit around the earth. I remember that time and much of what ensued. It all strikes me as quite remarkable, really.
RB in Canada.

Rusty Brown in Cda wrote:Try to imagine, if you will, how all this appears to a person who was a teenager when the word came out in October 1957 that the Russians had put a satellite into orbit around the earth. I remember that time and much of what ensued. It all strikes me as quite remarkable, really.
RB in Canada.

Well, I don't have to imagine! I was in my first year at the University of Toronto, walking along Bloor street, when a Toronto Telegram boy appeared with a stack of papers proclaiming Sputnik. And, years later, again on Bloor street, a small story in the paper saying that radio astronomers had measured the temperature of Venus --- and it was so hot that life (all those dinosaurs we had been imagining) was impossible. And vegetation on Mars went away. Arthur C. Clarke had even posited vegetation on the Moon! The solar system has been one disappointment after another. But!! There's still life under the ice of Europa? Or even on Titan? Hope springs eternal...

Your math is in error on the impact speed of the spacecraft Messenger. Moving at 4 miles per second equates to 14,400 miles per hour.

3.91 kilometers per sec is 8746 miles per hour; but on the Messenger web site, it gives the obit time of 8 hours 17 minutes and a very low altitude. The circumference of Mercury is 9525 which would give an obit speed of about 1200 miles per hour. Needs some clarification.

LeadHero wrote:
3.91 kilometers per sec is 8746 miles per hour; but on the Messenger web site, it gives the obit time of 8 hours 17 minutes and a very low altitude. The circumference of Mercury is 9525 which would give an obit speed of about 1200 miles per hour. Needs some clarification.

Messenger never flew anything remotely close to a circular orbit around Mercury.

Messenger crashed during perihermion.

LeadHero wrote:3.91 kilometers per sec is 8746 miles per hour; but on the Messenger web site, it gives the obit time of 8 hours 17 minutes and a very low altitude. The circumference of Mercury is 9525 which would give an obit speed of about 1200 miles per hour. Needs some clarification.

To clarify Art's comment, a body in an eccentric elliptical orbit is traveling fastest at periapsis, when it is closest to the body it is orbiting. Since MESSENGER impacted near periapsis, it was traveling at well above its average orbital speed. The lower average speed, as well as the highly eccentric orbit (meaning a longer orbital path) explains why the total orbital time can be longer than you expected.

Farewell, Messenger.

Well done, oh good and faithful robot.

Scott Kellogg

Sad to say litho-"breaking" may have been for appropriate from the day before.

Happy to say that Messenger's resting place will be remembered and hopefully commemorated for as long for as humans are around. Wonder if it will ever be visited as Apollo 12 landed near the Surveyor 3 site? We are a curious lot if for no other reasons.
Any ways R.I.P. Even though it may be" pieces".

I expect Messenger's final resting "place" to be a widely diffused 3D distribution, something like a 2D normal distribution along Mercury's surface and a Poisson distribution beneath it. And lots of teeny little pieces. One normally conceives of "coming to rest" as occurring at much less than three times the speed of a rifle bullet.

Bellerophon wrote:I expect Messenger's final resting "place" to be a widely diffused 3D distribution, something like a 2D normal distribution along Mercury's surface and a Poisson distribution beneath it. And lots of teeny little pieces. One normally conceives of "coming to rest" as occurring at much less than three times the speed of a rifle bullet.

There will be very little below the surface. The vast majority of material from a hypersonic impactor is ejected upwards, and settles in a surface blanket around the impact point.

Of course it's always mis-guided to kill the MESSENGER.

Shouldn't it be, rather, Messengers First Day ON Mercury

BMAONE23 wrote:Shouldn't it be, rather, Messengers First Day ON Mercury

Yesterday's and today's APOD; fabulous! Thank you all for comments made, so far. From speed corrections to first day of being back on firma after many years of no firma (Terra Firma to Mercurius Firma?) Having never read Vonnegut, Art has now enticed me to find out more about what to expect from his vacation highlights.

Thank you all for your comments.

Bill

Edit 1 changed Merca to Mercurius. Still looking for a best term.

First rock from the sun??

Good job, Messenger!!!! Hope they send another probe.

I hope to see a photo of the CRASH AREA with the new crater.... but that is probably just me...

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Also...."Newest Crater on Mercury"...

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Did they keep up their Anti Collision Insurance Policy with Mercury Insurance?