NASA spacecraft trying to get into Mercury's orbit

Mar 17, 2011
This image released by NASA shows an enhanced photo image of Mercury from its Messenger probe’s 2008 flyby of the planet. NASA says it was a taste of pictures likely to come after March 17, 2011, when the probe enters Mercury’s orbit. This photo shows the eastern part of the smallest and closest planet in our solar system. The colors in this picture are different than what would be seen with the naked eye, but show information about the different rock types and subtle color variations on the oddball planet. The bright yellow part is the Caloris impact basin, which is the site of one of the biggest in the solar system. Earth is about to get better acquainted with its oddball planetary cousin. (AP Photo/NASA/Johns Hopkins University Applied Physics Laboratory/Arizona State University/Carnegie Institution of Washington)

A desk-sized NASA spacecraft is riding the brakes all the way to Mercury, about to pull a tricky maneuver Thursday night to become the first man-made object to orbit the tiny planet.

After a trip of 4.9 billion miles and nearly six-and-a-half years, the will try to careen into an egg-shaped orbit and fight off the gigantic of the sun. To do so, it will have to use more than half of the fuel it was launched with in 2004 to reduce speed dramatically in just fifteen minutes.

If all works well, Messenger will circle as close as 120 miles from the surface and survey the entire planet for a year, beginning April 4. It will learn about Mercury's mysterious and - most tantalizing of all - discover if the closest-planet-to-the-sun has ice in its permanently dark frigid craters near its poles.

If all doesn't go well, it is more likely that the $446 million spacecraft flies away from and ends up circling the sun. should know whether they succeed in about an hour.

Making it difficult has been the sun's gravity and its incredible heat, forcing the probe to have large sunshades, said mission systems engineer Eric Finnegan. Messenger has had to take the long way around to get into Mercury's orbit because it has to continuously slow down and burn energy to get to the right place. While other spaceships have whipped around planets like a slingshot to speed up, Messenger has had to do just the opposite, going around Earth, Venus and Mercury to slow down.

"You're playing this incredible game of cosmic billiard balls to make this all work out," said Johns Hopkins University astronomer Ralph McNutt, who is a mission scientist.

If something goes wrong, engineers have fallback plans they can use in the next three days to three months to try to get the spacecraft back in some kind of orbit around Mercury.

NASA is shuttering the cameras on the spacecraft during the maneuver so there will be no pictures of the arrival, said mission chief scientist Sean Solomon.

Messenger has flown by Mercury a few times in its torturous trip there and Mariner 10 flew by there 36 years ago.

"Mercury has been called the forgotten planet because it's been so long since we sent a there," Solomon said.

But that is about to change.

Explore further: NASA asteroid defense program falls short: audit

More information: Messenger spacecraft: http://bit.ly/eqUYR8

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User comments : 12

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SincerelyTwo
not rated yet Mar 17, 2011
Whoa! Mercury has ice on it? I had no idea. Is there a very comfortable room temperature sweet spot somewhere in the gradient? :D

We should put satellites around every single planet!
Zephyr311
not rated yet Mar 17, 2011
Yes, the ice thing is surprising for me too. Really shows how light and heat are linked...proximity to the heat source doesn't seem to be as big a factor... Yes, I agree--satellites to study all of the planets (maybe instead of the numerous war-based ones we have).
Shootist
not rated yet Mar 17, 2011
The poles. If there are permanent shadows at the poles, ice will probably be found.

We should send (wo)men to every planet we can land on, and the moons of those we cannot. Humanity's destiny is not on this lone world we call Dirt.
GSwift7
5 / 5 (1) Mar 17, 2011
If there are permanent shadows at the poles, ice will probably be found


according to the wiki page, we 'may' already have seen the ice back in the 1990's with radar telescopes.

We should send (wo)men to every planet we can land on


Since it is so close to the Sun and there is almost no magnetic field or atmosphere on Mercury, it would be a very dangerous place to visit; we should send lawyers and politicians.
eachus
5 / 5 (2) Mar 17, 2011
Since it is so close to the Sun and there is almost no magnetic field or atmosphere on Mercury, it would be a very dangerous place to visit; we should send lawyers and politicians.


Why would you want to send gasbags to Mercury? There is no atmosphere there. I'm sure they would be more useful floating around Venus or Saturn.
yyz
5 / 5 (1) Mar 17, 2011
There will be a live webcast of the event from the Applied Physics Laboratory at Johns Hopkins Thursday beginning at 7:55 PM EDT: http://messenger....bit.html

MESSENGER Orbit Insertion is planned for 8:45 PM EDT.

After 6 1/2 long years, I'm not gonna miss this.
yyz
5 / 5 (1) Mar 17, 2011
"Whoa! Mercury has ice on it?"

http://nssdc.gsfc...ury.html

http://en.wikiped...phere.29

I'm hoping (fingers crossed) that some of these deposits will be visible, by optical imaging, down inside these craters, though they may be covered with a thin layer of regolith.

But other instruments on board will be used to detect signatures of (probably water) ice.
scidog
5 / 5 (1) Mar 18, 2011
when i was a kid in the 50's we were told it would be hot enough on mercury to melt lead.if no pools of hot lead are found i'm going to very disappointed.
neiorah
not rated yet Mar 18, 2011
I'll bet the ice is not water though.
Zephyr311
not rated yet Mar 18, 2011
I'll bet the ice is not water though.


Yep, which in my limited understanding makes it even a bit freakier since other gases which turn to ice usually do so at colder temps than H2O.
GSwift7
not rated yet Mar 18, 2011
Actually, it is likely to be at least partially water. IF I understand it correctly, I believe one theory is that gasses like hydrogen, oxygen and carbon could be released from rocks on the surface due to solar heating. Some of those gasses would drift into the dark craters where they would instantly condense and snow down to the crater floor. Over a long enough time it could be a significan amount of ice. If the temperature inside the craters is around -150 C then that's plenty cold enough for both water and CO2 ice to build up. With no significant atmosphere, once ice forms in a crater there would be nothing to ever remove it.
yyz
not rated yet Mar 18, 2011
"Actually, it is likely to be at least partially water. IF I understand it correctly, I believe one theory is that gasses like hydrogen, oxygen and carbon could be released from rocks on the surface due to solar heating."

Yeah, the 2 significant sources for these ices would be outgassing and impacts from comets and asteroids, similar to what is proposed for Earth's Moon*.

I'm not really up on just what ices are probable (and non-ices are possible), but comets are known to be good sources of H2O (and the depolarized nature of the radar reflections is noted as an indicator of water ice).

"With no significant atmosphere, once ice forms in a crater there would be nothing to ever remove it."

My NSSDC* source notes:

"There are mechanisms for potential loss of ice, however. These include photodissociation, solar wind sputtering, and micrometeoroid gardening. The effects of these processes are not well-understood."

* http://nssdc.gsfc...ury.html