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Title: Phoenix Spacecraft Lands On Mars
Post by: Geoff on May 26, 2008, 04:58:18 AM
I love this stuff:  :)

Mars Craft Succeeds in Soft Landing
Phoenix to Begin Search for Signs of Life Beyond Earth
 
By Marc Kaufman
Washington Post Staff Writer
Monday, May 26, 2008; Page A01

The spacecraft Phoenix landed safely on Mars yesterday, making a hazardous soft landing on the planet's far north with all its scientific systems apparently intact and ready to begin an intensive new search for life beyond Earth.

After counting down the last stage of the descent by hundreds and then tens of nerve-racking meters, officials at Mission Control in Pasadena, Calif., announced that "Phoenix has landed," setting off a joyous celebration by the mission team.

"It could not have gone better, not in my dreams," said Barry Goldstein, NASA's project manager at the Jet Propulsion Laboratory in Pasadena.

The touchdown, at about 8 p.m. Eastern time, was the first successful soft landing on the Red Planet -- using a parachute and thrusters rather than protective air bags -- since the twin Viking missions in 1976. In all, six of 11 similar attempts by the United States, Russia and England ended in failure, so the Phoenix team awaited with enormous apprehension the outcome of the spacecraft's approach and landing.

Phoenix plunged into the thin Martian atmosphere traveling at more than 12,000 mph. Over the next seven minutes, friction -- which raised the temperature on the heat shield to 2,600 degrees Fahrenheit -- slowed it enough to deploy the parachute.

About half a mile from the surface, and with only seconds remaining before touching down, 12 small rocket thrusters fired to slow the lander's descent speed to 5 mph. Before it landed, however, Phoenix had to orient itself toward the sun to ensure that its solar panels could pick up enough light to generate the power it will need on the surface.

Peter Smith of the University of Arizona, lead investigator for the mission, said earlier that the entry would amount to "seven minutes of terror" for the scientists.

Like the Viking landers, Phoenix is designed to look for organic material and other signs that life has existed on Mars, or could exist on the planet. Unlike the two rovers that have been exploring the Martian surface for nearly five years, Phoenix is built to stay in one place and use its robotic arm to dig into the soil and ice. The vehicle is equipped with several miniature chemistry labs to analyze the material it digs up.

The lander touched down further north on Mars than any previous lander. NASA scientists think the frozen water on or near the surface may tell them whether the minerals and organic compounds needed for life as we know it exist, or have ever existed, on the planet.

Throughout the descent and landing, NASA engineers at the Jet Propulsion Laboratory were receiving data on the spacecraft's progress 15 minutes after events occurred -- helpless to intervene if anything went wrong. Transmissions were sent from Phoenix to the orbiting Mars Odyssey spacecraft, then relayed back to Earth at the speed of light over the 171 million miles between the planets.

Phoenix, named for the mythological bird reborn from its ashes, was assembled largely from parts manufactured for other spacecraft. After two Mars mission failures in 1999, the space agency scrapped a lander mission planned for 2000 and recycled some of the hardware.

One of those failures was the last time NASA tried a soft landing on Mars. The Mars Polar Lander was angling for the south pole when it prematurely shut off its engine and crashed to the surface below. The other failure involved a spacecraft that was supposed to go into orbit around Mars; NASA lost contact with it during the approach, and its fate is unknown.

The 900-pound, three-legged Phoenix lander, which cost $457 million, traveled a circuitous path of 423 million miles over almost 10 months to reach Mars. A rocket-and-parachute landing system -- like that of the Viking landers of 32 years ago -- was chosen because it allowed NASA to better pinpoint the landing location. The system is also a prototype of one that NASA hopes will one day land astronauts on Mars.

The later Mars Pathfinder and the two robot rovers, Opportunity and Spirit, which have been exploring the planet's equatorial region, landed using air bags to cushion the impact. Air bags are not practical for heavier craft such as the Phoenix because the weight of bigger bags reduces the amount of scientific equipment that can be carried.

The Phoenix was targeted at the north polar region because that is where some form of water (in the form of ice) is most likely to be present, and scientists believe that a form of water is necessary for life. They are convinced that surface water flowed on Mars billions of years ago, a conclusion reached by studying geologic features of the Martian landscape. Today, conditions on Mars do not allow for liquid water, in large part because the atmosphere is only 1 percent as dense as Earth's.

In 2002, however, the Mars Odyssey orbiter discovered that large amounts of water ice lay just beneath the surface in the permafrost that covers much of far northern Mars. Scientists say the region, which is notably flat and smooth, may have once been the bottom of a large ocean.

They are also intrigued that the surface shows polygonal patterns remarkably similar to some seen in Antarctica. Scientists speculate that they could be the result of cycles of freezing and thawing.

In addition to its sophisticated cameras, soil retrievers and mini-laboratories, Phoenix carried on its journey a mini-DVD created by the Planetary Society called "Visions of Mars." It holds a library of science fiction stories and art, as well as the names of more than 250,000 people.

The DVD, featuring the likes of Carl Sagan, Arthur C. Clarke and Ray Bradbury, is made of material designed to last for hundreds, if not thousands, of years.

http://www.washingtonpost.com/wp-dyn/content/article/2008/05/25/AR2008052502289.html?hpid=topnews

(http://i299.photobucket.com/albums/mm317/geoffw_2008/229999main_SS000EFF896228773_10CA8R.jpg)



Title: Re: Phoenix Spacecraft Lands On Mars
Post by: Bobber on May 26, 2008, 07:19:47 AM
Amazing.
Title: Re: Phoenix Spacecraft Lands On Mars
Post by: alexis on May 26, 2008, 03:42:18 PM
Photo looks like my friend's back yard in west Texas.

I think it's a conspiracy theory ...

 :)
Title: Re: Phoenix Spacecraft Lands On Mars
Post by: harihead on May 26, 2008, 06:36:34 PM
Alexis, this is clearly Arizona. That light dot near the horizon, magnified 10,000 times, is a road sign that reads, "Next gas 167 miles".

Geoff, thanks for posting this. I have a friend at JPL who devised the landing system for the rovers. I must congratulate him, as I'm sure he was lurking there somewhere when Phoenix landed. :)
Title: Re: Phoenix Spacecraft Lands On Mars
Post by: Hello Goodbye on May 28, 2008, 01:20:52 AM
Uh, oh!  Now we've done it!

(http://www.vfxhq.com/zarchive/1996/mars/mars1.jpg)
Title: Re: Phoenix Spacecraft Lands On Mars
Post by: Geoff on May 28, 2008, 01:38:00 AM
Quote from: 59
Uh, oh!  Now we've done it!

([url]http://www.vfxhq.com/zarchive/1996/mars/mars1.jpg[/url])


 ;D

... but perhaps a less worrying prospect than previously thought:

British U.F.O. Shocker! Government Officials Were Telling the Truth

By SARAH LYALL
Published: May 26, 2008

LONDON
Title: Re: Phoenix Spacecraft Lands On Mars
Post by: douglasleee on May 28, 2008, 03:15:11 AM
My deepest apologies for the following:

http://youtube.com/watch?v=mt70kcBosCI

(p.s. - I am a "space" nut (Star wars, Star Trek, landing on the moon in the 60's), but I could "HELP" myself on this
one. May JPGR forgive me.)
Title: Re: Phoenix Spacecraft Lands On Mars
Post by: harihead on May 28, 2008, 04:02:41 AM
Quote
the sight of a smallish
Title: Re: Phoenix Spacecraft Lands On Mars
Post by: Geoff on May 28, 2008, 04:55:38 AM
Quote from: 1161
Out fishing in 1983, the man had just poured himself a cup of tea, he recalled, when he was approached by two four-foot-tall beings wearing pale green overalls and large helmets. They led him into what turned out to be their ship
Title: Re: Phoenix Spacecraft Lands On Mars
Post by: douglasleee on May 28, 2008, 05:20:33 AM
I wish I could say I've seen a/an "UFO", but haven't. I also would like to see an extraterrestrial and ask a few question.
BUT!!! I think our planet (not speaking of the people in this forum, of course) is to "war-like" and to ignorant for them
to want to land and say "look - We exist, you're not alone."
Title: Re: Phoenix Spacecraft Lands On Mars
Post by: BlueMeanie on May 28, 2008, 09:59:21 AM
If anyone is out there, and is capable of reaching our planet, then they are thousands of years, probably millions, more advanced than us. If we're lucky, and they're friendly, I expect they'd just want to observe evolution. If they're not, they could probably destroy us with one swipe.
Title: Re: Phoenix Spacecraft Lands On Mars
Post by: Geoff on May 28, 2008, 03:17:41 PM
I think biology, probability, and physics are all against UFO's existing. There are obviously all sorts of fascinating things out in space, including whole realms of matters we can't even guess at yet, but humanish creatures in mechanical contraptions aren't going to be among the things to turn up.
Title: Re: Phoenix Spacecraft Lands On Mars
Post by: harihead on May 28, 2008, 04:41:46 PM
Geoff, Geoff, haven't you watched Star Trek? There are honey cloud creatures, and giant amoebas out in space-- all kinds of things, not just scantily clad women in silver bikinis. ;D

Actually, it is fascinating to speculate on extraterrestrial life. I'm a little concerned that SETI hasn't turned up anything yet. You'd think if there were other civilizations, we'd get a sniff of their transmissions-- unless their technology is too sophisticated for us to pick up. Life is actually pretty easy to evolve (they've managed it several times in the lab), but the accidents that might lead to a particular kind of intelligent rat building a spaceship are rather more statistically remote. And then we've got to time it. 3 billion years of development to get machine-building humans, and we've had a space-capable society for about 45 minutes?

Still, I like Rodenberry's vision of a universe filled with fun things. He might be right-- but getting us and them in the same place at the same time might be tricky.
Title: Re: Phoenix Spacecraft Lands On Mars
Post by: douglasleee on May 29, 2008, 01:25:57 AM
I have to agree with Geoff on the 'Transportation" part of it. We can't even agree between Einstein (you can't travel faster
than light) and Roddenberry warp travel. It would be nice if it could be done, but I think we're just not there yet (knowing
how to do it, IF it exist.) On the other part, If there is a tree on some sort of planet out there somewhere, that is some
sort of "life" to me. Also, finding SETI is like our own car radio, we just have to find the correct "station" that they are
broadcasting on and look at all of those radio channels.  And maybe they sent a signal back in 1492, when we didn't have
about radio. The acting in "CONTACT" wasn't great, but I loved Jodie Foster "dad" in this movie - "if we're alone, it's an awful lot of wasted space." Call me "wishful thinking", I call it "continually learning".
Title: Re: Phoenix Spacecraft Lands On Mars
Post by: Geoff on May 29, 2008, 03:40:34 AM
Quote from: 551
Life is actually pretty easy to evolve (they've managed it several times in the lab), but the accidents that might lead to a particular kind of intelligent rat building a spaceship are rather more statistically remote. And then we've got to time it. 3 billion years of development to get machine-building humans, and we've had a space-capable society for about 45 minutes?

Exactly: the UFO hypothesis rests on the argument that the chemical and biological evolution of earth was duplicated independently on an alien world and to such an extent that it not only produced a species that thought like we did but evolved a technological capability that we would recognize as such at approximately the same time as us. A coincidence like that would be truly staggering, even in a galaxy with perhaps a hundred million Earth type planets. Then there's the distances involved and the whole speed of light problem.

Personally I'm all for the Roddenberry sort of thing myself, and not just because of all the women in scantily clad bikinis (good selling point that, actually), but I don't think a Star Trek sort of future is at all plausible. Not that any consideration like that stops me from watching the old '60s show: I've got a complete set of it on DVD.  ;D


Title: Re: Phoenix Spacecraft Lands On Mars
Post by: douglasleee on May 29, 2008, 06:06:41 AM
It would be "truly staggering" to duplicate humans, in the same time frame and have them "in a sense" past us in a
technological area (here's where they would "past" us and wouldn't be in the same time frame as us. i.e be able to
travel threw space "more at easy" than us.) I most humbly take the other view point, a far more advanced culture would
have to exist to create this "space travel", and since our solar system is only about 4.5 million years and the Universe is
about 13-14 billion, I can't remove that possiblity. I view the oppsite of Geoff, how can there "not" be something out there
besides us, but as far as "earthlings" right now are concerned, the "proof" leans towards Geoff side. The "travel" part, I
totally agree upon - I have to leave this up to Science and the SciFi crowd.
Title: Re: Phoenix Spacecraft Lands On Mars
Post by: Kevin on May 29, 2008, 08:38:28 AM
Quote from: 1161
I think biology, probability, and physics are all against UFO's existing. There are obviously all sorts of fascinating things out in space, including whole realms of matters we can't even guess at yet, but humanish creatures in mechanical contraptions aren't going to be among the things to turn up.

Here here. Thew whole idea is prepostorous. Funny how the whole UFO mania thing happened immediately after World War Two and the advent of jet propulsion, and all look remarkably like the original fiction flying saucer in that movie I can't remember.
We have not identified any planets likely to substain life (of the pitifully few we have discovered.) The chances of them evolving life that can build spaceships and listen to radio signals is just silly.
Maybe for life to exist it needs a bizarre set of circumstances - the right sized planet of the right age next top the right sun. Perhaps the odds of that are a billion to one. We could just be very lucky.
Title: Re: Phoenix Spacecraft Lands On Mars
Post by: BlueMeanie on May 29, 2008, 10:33:12 AM
Quote from: 185

Here here. Thew whole idea is prepostorous. Funny how the whole UFO mania thing happened immediately after World War Two and the advent of jet propulsion, and all look remarkably like the original fiction flying saucer in that movie I can't remember.
We have not identified any planets likely to substain life (of the pitifully few we have discovered.) The chances of them evolving life that can build spaceships and listen to radio signals is just silly.
Maybe for life to exist it needs a bizarre set of circumstances - the right sized planet of the right age next top the right sun. Perhaps the odds of that are a billion to one. We could just be very lucky.

I'm afraid this is where I'm going to have to disagree with you Kev. The possibilities of intelligent life existing on other planets are immense. If life could eveolve on this little planet, then why not somewhere else? I don't expect 'aliens' to look like humans, in fact if we ever met any we may not even recognise them as living life forms.

I don't think we've ever been visited by beings from outer space, but I don't discount the possibility of it happening sometime in the future. Though if you had the ability to travel through interstellar space, why would you want to land here?

The problem is, we're a 'Type 0 Civilisation', and most of us think like people who are from a 'Type 0 Civilisation'. Because we can't do it, or it breaks the laws of 'our' physics, then it can't be possible.

I don't think we're going to discover life on another planet until we become a 'Type 1 Civilisation', and that won't happen for at least a hundred years. We just don't have the technology for it. I don't think they'll be coming to us.
Title: Re: Phoenix Spacecraft Lands On Mars
Post by: Geoff on May 29, 2008, 12:12:00 PM
I think you have to separate the whole UFO thing from the broader question of what might exist out in the universe. UFO's can be discounted on the grounds of improbability, lack of evidence, and the sheer foolishness of the vast majority of their proponents. What may or may not exist in the universe, including life as we understand it, intelligent or otherwise, is another matter altogether. Here I think the possibilities are open to an extent that's actually mind boggling and quite possibly even beyond our conceptual capabilities entirely. We're creatures of one very small and particular place trying to grasp something that's almost infinitely larger and more varied, and my basic objection to the whole UFO thing, apart from what I've said above, is the spectacular lack of imagination that's implied.
Title: Re: Phoenix Spacecraft Lands On Mars
Post by: Kevin on May 29, 2008, 12:17:53 PM
Quote from: 1161
my basic objection to the whole UFO thing, apart from what I've said above, is the spectacular lack of imagination that's implied.

Oh yeah baby. I love the arguement when people say "well life on other planets is probably not something we'd recognise" yet expect us to believe that they are similar enough to develope metalurgy, physics, engineering and build remarkably human like spaceships.
Like BM says there is a possibility of some life on other planets, but as for it building ships etc....
Title: Re: Phoenix Spacecraft Lands On Mars
Post by: Geoff on May 29, 2008, 12:39:54 PM
Quote from: 185
Oh yeah baby. I love the arguement when people say "well life on other planets is probably not something we'd recognise" yet expect us to believe that they are similar enough to develope metalurgy, physics, engineering and build remarkably human like spaceships.
Like BM says there is a possibility of some life on other planets, but as for it building ships etc....

People can't imagine anything other than themselves, except maybe themselves with funny ears or light sabers flying mechanical contraptions. That sort of thing is the least likely possibility, I think.

Title: Re: Phoenix Spacecraft Lands On Mars
Post by: Hello Goodbye on May 29, 2008, 02:38:51 PM
Quote from: 1161
Personally I'm all for the Roddenberry sort of thing myself, and not just because of all the women in scantily clad bikinis......

Silver bikinis, Geoff!     ;)
Title: Re: Phoenix Spacecraft Lands On Mars
Post by: harihead on May 29, 2008, 04:06:31 PM
^^ That's right, let's stick to the known facts. ;D

Quote from: 1161
People can't imagine anything other than themselves, except maybe themselves with funny ears or light sabers flying mechanical contraptions. That sort of thing is the least likely possibility, I think.
Exactly. For practical purposes, the reasons most aliens look like humans is because the show producers are casting humans for the roles. The reasons so many of those aliens have doofy foreheads is because the prosthetic for the forehead does not greatly limit the actor's ability to express emotion, which happens mainly on the lower part of the face. But those are the aliens that people see on TV and in movies, so those are the aliens people keep expecting to see.

I was being only slightly facetious when I was talking about giant amoebas in space. I think it's far more practical to warp space and pop out where you want to be than to put yourself in a tin can and travel for generations in it to find someplace nice to settle. Although that all makes great fiction-- especially when the new ships are faster than the old ships so the later arrivals get there first. Cool to think about. We do what we can do, and our imagination is limited by our culture and technological development.
Title: Re: Phoenix Spacecraft Lands On Mars
Post by: alexis on May 29, 2008, 05:57:15 PM
Quote from: 483

 I don't expect 'aliens' to look like humans, in fact if we ever met any we may not even recognise them as living life forms.
 


I have my suspicions about this specific can of Chef Boyardee I've just warmed up, it doesn't seem like all the other cans. It seems somehow ... aware ...

I know it's silly, but maybe I should just put it back and eat another one instead. I would not want to be the first one to commit extraterrestrial murder, much less then be accused of eating the victim. Oh no, I've got all kinds of Chef Boyardee in my fridge, if they were all sentient, it would make me look like some kind of  intergalactic Jeffrey Dahmer (chainsaw)

That is awfully farfetched though, and I am pretty busy now. Still ... No, I think I'll just stop being silly and eat this one.

Well, here goes ...
Title: Re: Phoenix Spacecraft Lands On Mars
Post by: Hello Goodbye on May 29, 2008, 07:16:11 PM
Quote from: 551
^^ That's right, let's stick to the known facts. ;D

Precisely.

(http://home.att.net/~thorobred7/silverbikini.JPG)

Title: Re: Phoenix Spacecraft Lands On Mars
Post by: harihead on May 29, 2008, 07:40:27 PM
LOL! That's exactly the episode I was thinking of. I had this friend who, whenever he came over, put on "The Gamesters of Triskelion". He had a huge crush on Shahna.

Alexis, go ahead and eat. Just remember the salad scene in Alien. That's all I'm saying...
Title: Re: Phoenix Spacecraft Lands On Mars
Post by: alexis on May 29, 2008, 08:19:02 PM
Salt. Need salt.
Title: Re: Phoenix Spacecraft Lands On Mars
Post by: alexis on May 29, 2008, 08:27:25 PM
Salt. Need salt.
Title: Re: Phoenix Spacecraft Lands On Mars
Post by: pc31 on May 30, 2008, 04:06:25 AM
i believe there is life on other planets,maybe not in our immeadate universe but out there....there maybe even be something occuping the same space as me at a different vibratory rate.....there are somethings about clearly not of this earth....
Title: Re: Phoenix Spacecraft Lands On Mars
Post by: douglasleee on May 30, 2008, 04:14:49 AM
Geoff - (If the electro's in my brain just would fire 100% of the time -- haha)

What would you think, for example, if one of these "ufo's" were like a "dron" aircraft, sent by an alien, but it was
"unmanned" and just sent to see what was on Earth - sending results back to the place of origin? Granted, the
travel alone is still in your favor. Not much different from the Phoenix, but ....... (P.S. I haven't seen all of "The
Blackadder" or 'Mr. Bean" but I'm "catching up" as quick as I can!!)
Title: Re: Phoenix Spacecraft Lands On Mars
Post by: Geoff on May 30, 2008, 09:42:46 AM
Quote from: 551
We do what we can do, and our imagination is limited by our culture and technological development.

Arthur C Clarke quoted this from JBS Haldane on more than one occasion:

I have no doubt that in reality the future will be vastly more surprising than anything I can imagine. Now my own suspicion is that the Universe is not only queerer than we suppose, but queerer than we can suppose.

That's it exactly, I think.  :)
Title: Re: Phoenix Spacecraft Lands On Mars
Post by: Geoff on May 30, 2008, 09:53:06 AM
Quote from: 1285
What would you think, for example, if one of these "ufo's" were like a "dron" aircraft, sent by an alien, but it was
"unmanned" and just sent to see what was on Earth - sending results back to the place of origin? Granted, the
travel alone is still in your favor. Not much different from the Phoenix, but

Have a look at the Haldane quote above. A robot probe is the sort of thing we'd do: it's not out of the question, of course; but my point is that whatever's out there in space, assuming there's anything like intelligent life in the sense we mean it, wouldn't be doing the same sorts of things were doing: they're aliens, after all, the end products of a completely separate line of evolutionary development. They probably wouldn't think like us at all or produce a technology we'd even recognize as such.  :)
Title: Re: Phoenix Spacecraft Lands On Mars
Post by: Geoff on June 01, 2008, 02:35:21 AM
Mars' Water Appears To Have Been Too Salty To Support Life

ScienceDaily (May 30)
Title: Re: Phoenix Spacecraft Lands On Mars
Post by: Geoff on June 02, 2008, 06:06:30 AM
Camera On Arm Looks Beneath NASA Mars Lander

ScienceDaily (Jun. 1)
Title: Re: Phoenix Spacecraft Lands On Mars
Post by: alexis on June 02, 2008, 03:34:32 PM
Quote from: 1161
Mars' Water Appears To Have Been Too Salty To Support Life

ScienceDaily (May 30)
Title: Re: Phoenix Spacecraft Lands On Mars
Post by: pc31 on June 03, 2008, 03:55:09 AM
Quote

([url]http://i299.photobucket.com/albums/mm317/geoffw_2008/080531231836-large.jpg[/url])

just as i thought.........isn't that an audi track on the right???

Title: Re: Phoenix Spacecraft Lands On Mars
Post by: DaveRam on June 03, 2008, 10:47:26 AM
I've seen a UFO , i saw it with my mum and she never touches the weed (jumping)
Title: Re: Phoenix Spacecraft Lands On Mars
Post by: Geoff on June 03, 2008, 03:48:37 PM
Quote from: 971
I've seen a UFO , i saw it with my mum and she never touches the weed (jumping)


Never mind UFO's; when I see one of these schlepping up the road, I'll be convinced.  ;D

(http://i299.photobucket.com/albums/mm317/geoffw_2008/simpsons0sw.png)

Title: Re: Phoenix Spacecraft Lands On Mars
Post by: BlueMeanie on June 04, 2008, 08:30:46 AM
Quote from: 1161

Never mind UFO's; when I see one of these schlepping up the road, I'll be convinced.  ;D

([url]http://i299.photobucket.com/albums/mm317/geoffw_2008/simpsons0sw.png[/url])



Mother!!!
Title: Re: Phoenix Spacecraft Lands On Mars
Post by: Geoff on June 26, 2008, 11:54:55 AM
This is interesting:  :)

Largest Crater In Solar System Revealed By NASA Spacecraft

ScienceDaily (June 26) — New analysis of Mars' terrain using NASA spacecraft observations reveals what appears to be by far the largest impact crater ever found in the solar system.

NASA's Mars Reconnaissance Orbiter and Mars Global Surveyor have provided detailed information about the elevations and gravity of the Red Planet's northern and southern hemispheres. A new study using this information may solve one of the biggest remaining mysteries in the solar system: Why does Mars have two strikingly different kinds of terrain in its northern and southern hemispheres? The huge crater is creating intense scientific interest.

The mystery of the two-faced nature of Mars has perplexed scientists since the first comprehensive images of the surface were beamed home by NASA spacecraft in the 1970s. The main hypotheses have been an ancient impact or some internal process related to the planet's molten subsurface layers. The impact idea, proposed in 1984, fell into disfavor because the basin's shape didn't seem to fit the expected round shape for a crater. The newer data is convincing some experts who doubted the impact scenario.

"We haven't proved the giant-impact hypothesis, but I think we've shifted the tide," said Jeffrey Andrews-Hanna, a postdoctoral researcher at the Massachusetts Institute of Technology in Cambridge.

Andrews-Hanna and co-authors Maria Zuber of the Massachusetts Institute of Technology, and Bruce Banerdt of NASA's Jet Propulsion Laboratory in Pasadena, Calif., report the new findings in the journal Nature this week.

A giant northern basin that covers about 40 percent of Mars' surface, sometimes called the Borealis basin, is the remains of a colossal impact early in the solar system's formation, the new analysis suggests. At 8,500 kilometers (5,300 miles) across, it is about four times wider than the next-biggest impact basin known, the Hellas basin on southern Mars. An accompanying report calculates that the impacting object that produced the Borealis basin must have been about 2,000 kiolometers (1,200 miles) across. That's larger than Pluto.

"This is an impressive result that has implications not only for the evolution of early Mars, but also for early Earth's formation," said Michael Meyer, the Mars chief scientist at NASA Headquarters in Washington.

This northern-hemisphere basin on Mars is one of the smoothest surfaces found in the solar system. The southern hemisphere is high, rough, heavily cratered terrain, which ranges from 4 to 8 kilometers (2.5 to 5 miles) higher in elevation than the basin floor.

Other giant impact basins have been discovered that are elliptical rather than circular. But it took a complex analysis of the Martian surface from NASA's two Mars orbiters to reveal the clear elliptical shape of Borealis basin, which is consistent with being an impact crater.

One complicating factor in revealing the elliptical shape of the basin was that after the time of the impact, which must have been at least 3.9 billion years ago, giant volcanoes formed along one part of the basin rim and created a huge region of high, rough terrain that obscures the basin's outlines. It took a combination of gravity data, which tend to reveal underlying structure, with data on current surface elevations to reconstruct a map of Mars elevations as they existed before the volcanoes erupted.

"In addition to the elliptical boundary of the basin, there are signs of a possible second, outer ring -- a typical characteristic of large impact basins," Banerdt said.

http://www.sciencedaily.com/releases/2008/06/080625223036.htm