• Server Outage Announcement

    Hello, Everyone.
    We will be installing an update to XenForo (the forums software), and doing some server maintenance.
    Consequently, the forums will be unavailable from about 12 - 2 MDT / 2 - 4 EDT / 6 - 8 GMT on Sunday 9th May 2021.

The Planet Mars: Scientific Findings & Conjectures

rynner2

Gone But Not Forgotten
(ACCOUNT RETIRED)
Joined
Aug 7, 2001
Messages
55,231
Reaction score
9,151
Points
284
Mars mystery
The height of the interior mound of sediment inside this crater exceeds the crater rim heights by 900 meters (3,000 ft). This is a confounding problem. How does all this material get inside this crater and actually rise higher than its holding chamber? What is this material? Where did it come from? Why is it still here? It is exactly these kinds of enigmas that makes Mars so very interesting.
marstoday.com/viewsr.html?pid=9390 for piccies.
LInk is obsolete. The report has moved to another website:
http://spaceref.com/news/viewsr.html?pid=9390


Mars Odyssey THEMIS Image: Bizarre Crater Mound
Status Report From: Mars Odyssey THEMIS
Posted: Thursday, June 5, 2003
 
Last edited by a moderator:
A

Anonymous

Guest
It is probably a bit premature to say that this is sediment-

Surely it could be some sort of igneous formation, which has swollen out of the crust as a response to the meteor impact?

Although it could perhaps be a dome of ice expanding underground, like happens on this planet sometimes (on a much smaller scale)-

but sediment?
 

Mama_Kitty

Gone But Not Forgotten
(ACCOUNT RETIRED)
Joined
Apr 4, 2002
Messages
352
Reaction score
56
Points
59
http://uk.news.yahoo.com/040205/12/elae3.html
Thursday February 5, 02:00 PM

Perfect spheres seen in Mars soil
By David L Chandler, Pasadena

Thousands of tiny, perfectly rounded spheres have been seen on the dark soil around the Mars rover Opportunity.

The bead-like particles were seen in high-resolution images taken by the craft's panoramic camera, and two of them were seen close up by its microscopic imager.

"The spheres are unlike anything we've ever seen on Mars," said lead scientist Steven Squyres, and are intriguing because "there are only so many ways to make round things".

They could be frozen drops of lava ejected by a volcanic eruption (called lapillae), frozen drops of rock melted and thrown out by a meteorite impact (called tektites), or, most excitingly, particles formed by slow chemical accretion in a body of water (called oolites).

Further close examination by the rover's suite of instruments should help to pinpoint the mechanism of formation. For example, if the rover finds a cracked sphere and sees pearl-like concentric layering, the particles would be oolites.

However, some of the spheres appear to have holes in them, which suggests the escape of trapped gases from a molten blob and hence a volcanic or impact origin.

Field trip

In addition to the spheres, there are other pebbles on the surface that have a reddish colour. While much of Mars is covered in red dust, the underlying rocks are mostly dark, making these pebbles unusual. They may be weathering out of the outcrop of bedrock six metres from the lander.

In the early hours of Thursday morning, Opportunity moved about three metres forward, bringing it about halfway to the right-hand edge of the long outcrop. It is expected to complete the trip on Friday.

The rover will then spend several days travelling slowly along it, taking high-resolution, full-colour stereo images and infrared spectra of the finely layered rocks. These images will be then used to guide the science team in deciding which areas to investigate up close with the rover's multiple instruments.

A detailed image already taken by the mini-TES infrared spectrometer shows some parts of the 22-metre crater in which Opportunity landed are very rich in hematite while others have virtually none. The presence of the iron-oxide mineral, which often forms in liquid water, was a major factor in choosing Opportunity's landing site.

"Every shape, texture and colour has a story to tell" about the geological history of the area, said Squyres. "In the coming days, we'll unravel the mysteries."
 
A

Anonymous

Guest
Not sure, but this is the only piccie I can find on the Nasa Web site of the microscopic structures in the soil.

They don't look very perfect or even spherical to me - have a look.

Mars Soil Picture

Are there any more pictures anyone can find?
 

naSTEe

Gone But Not Forgotten
(ACCOUNT RETIRED)
Joined
Jul 24, 2002
Messages
133
Reaction score
0
Points
47
whats the point in news agencies reporting these things without any photographic evidence, its just words otherwise, and they lie easier than the camera does
 

TheGord

Gone But Not Forgotten
(ACCOUNT RETIRED)
Joined
Aug 19, 2003
Messages
57
Reaction score
0
Points
37
Martian Marbles

I notice the small spheroid on the right seems to have a hole in it - making it a volcanic object. Still, could be a good market in the future for martian marbles....:)
 
A

Anonymous

Guest
Re: Martian Marbles

TheGord said:
I notice the small spheroid on the right seems to have a hole in it - making it a volcanic object. Still, could be a good market in the future for martian marbles....:)
It could well be some form of volcanic glass. Or, glass made from fused sand, thrown out by a meteor impact, tectites.
 
A

Anonymous

Guest
Banyan Trees/Glacial Lakes on Mars

What is everyone's take on the banyan trees on Mars-FT had the photo's a few years back, Now UFO magazine have a whole article on them and yes they really really do look like vegatation. There are also some intriquing pics of what really do look like glacial lakes. Even Arthur C Clark give the Banyan theory credence-which reminds me, what was that pic around the same time of a bridge on one of the moons of Jupiter that Mr. Clarke was impressed by.
P.S Anyone have a picture of an X-Drone on the moon?
 
A

Anonymous

Guest
Banyan Tree/Glacial Lakes

JerryB,
Have you seen the Banyan tree/Glacial Lake photo's? They are very clear and high def.
And lets remember this whole site is about possible anomolies/strange phenomena.......
I do agree that it does kinda go into the Face on Mars territory and yes, UFO magazine is not exactly the Skeptical Inquirer, but it's the only magazine that I know FT readers in the UK could look at these pictures, although I guess the Cydonia/Enterprise mission web sites will have them......
 

Jerry_B

Gone But Not Forgotten
(ACCOUNT RETIRED)
Joined
Apr 15, 2002
Messages
8,055
Reaction score
59
Points
129
Yes, I have seen the photos - but just because something looks similar to something else doesn't mean much in this sort of situation. What's being seen could of course be some natural, but as yet not understood, geological object. As Mars has only been viewed most of the time via imagery, there's always the chance that a viewer's mind will make connections and see patterns in things which maybe aren't there. It's similar to what could happen if someone saw aerial photos of the Giants Causeway, but didn't have any idea about how such a thing could've arisen through natural processes. Mars is, of course, not like Earth - all sorts of things could be going on, but they may not be due to organic life of some sort (i.e. plants).
 
A

Anonymous

Guest
Devils Causeway Photo?

Does anyone have a photo of Devils Causeway from space/orbit?
 
A

Anonymous

Guest
Banyan trees may actually be just that

A scientist who identifies these kind of things from ariel photo's who was shown these photo's cold ( i.e not told they were from Mars) basically said that they were a network of ancient tree's with a large root above ground the type that flourish in dry soil. areas i.e Banyan trees in India, Indonesia etc
So there you have it......dunno what anyone else makes of that?
 

KeyserXSoze

Gone But Not Forgotten
(ACCOUNT RETIRED)
Joined
Jun 2, 2002
Messages
946
Reaction score
14
Points
49
Glints

http://www.newscientist.com/news/news.jsp?id=ns99994752
Beagle 2 may have sped to its death


17:52 08 March 04

NewScientist.com news service

The missing Beagle 2 lander may have crunched into the Martian dust after plummeting through an unexpectedly thin atmosphere.

New measurements from the spacecraft's mothership, Mars Express, suggest the upper atmosphere can be far less dense than anyone thought. This could have been fatal for the lander because it relied on the atmosphere's braking effect to trigger the release of its parachute.

If the main parachute opened too late, the probe would have the hit the ground too fast to survive. It may even have failed to inflate the airbags intended to cushion its landing.

But this was only one of many gloomy scenarios that the project scientists are considering to explain why the probe has been silent since it was ejected from Mars Express on 19 December.

"We're analysing all the possible failure modes - and there are an awful lot", said Mark Sims, of the University of Leicester, UK, at a meeting in London on Monday.


Rapid fluctuation


Other atmospheric factors being considered include turbulence. After NASA's rover Spirit landed it measured the temperature of the atmosphere in the kilometre above it.

The temperature was fluctuating very rapidly - on a timescale of seconds. If the same thing was happening at the Beagle 2 landing site, the severe turbulence could, says Sims, have collapsed the parachute.

Another line of investigation has been prompted by a picture of Beagle 2, snapped as it was ejected from Mars Express. The receding probe is half in shadow, but within the shadow there is a bright glint. This is cause for concern because the probe's surface should be smooth.

"It may be nothing, it could be everything" said Sims. The object could be one of the explosive bolts used to secure the probe to its host during take-off. More worryingly, it could be something that broke off Beagle 2, or a wrinkle in the insulation wrapping the probe.

Scouring the surface

Whilst the team analyse these scenarios, a NASA satellite is being used to scour the surface of Mars for signs of the lander. The camera on the Mars Global Surveyor, with a resolution of 1.6 metres per pixel, should be able to spot the remnants of the parachutes, air-bags or even the white shell that enclosed Beagle 2's innards. The camera has already been used to pin-point the positions of the NASA rovers, Spirit and Opportunity.

About half of Beagle 2's 60-kilometre-long landing ellipse has now been scanned, and bright white pixels have been picked out in two images, taken near the end of February.

In one, the white spots sit on the rim of a crater. These may turn out to be boulders. The second image shows four white pixels in a line. Dubbed the "string of pearls", this could be the lander, perhaps entangled in its parachute. But it is more likely that the "pearls" were produced by noise in the camera, perhaps caused by cosmic rays.

However the Beagle 2 team have asked for a higher resolution close-up of the "string of pearls", and more pictures will be taken this week. It is a race against time, says Colin Pillinger, the lander's lead scientist: "We run the risk that by the end of March a thin veneer of dust may have covered up the evidence."

Finding debris on the surface might at least reveal at what stage the mission failed. But if neither of the probe's two parachutes opened, Beagle 2 may be forever undetectable - buried in a crater of its own making.

Jenny Hogan
 

sunspot8

Gone But Not Forgotten
(ACCOUNT RETIRED)
Joined
Apr 3, 2004
Messages
61
Reaction score
0
Points
22
Opportunity Spots Curious Object On Mars

http://www.space.com/missionlaunches/ma ... 50113.html

NASA’s Opportunity Mars rover has come across an interesting object -- perhaps a meteorite sitting out in the open at Meridiani Planum. Initial data taken by the robot’s Mini-Thermal Emission Spectrometer (Mini-TES) is suggestive that the odd-looking “rock” is made of metal.
 

headnspace

Gone But Not Forgotten
(ACCOUNT RETIRED)
Joined
Sep 6, 2001
Messages
154
Reaction score
4
Points
49
preliminary results = "metal"

"metal" tells us very little. Iron? Copper?

So, my first impression is that it's a part of the lander that broke off and fell nearby.

My next impression is that it's a Meteor fragment that fell nearby.

My next impression is that "It's just a metallicy rock" of martian origin that happens to be nearby.

My last impression is that it's a piece of Mars that broke off when the lander landed, and fell nearby.

Tough being in astronomy. . . always "more research needed." ;)
 

sunspot8

Gone But Not Forgotten
(ACCOUNT RETIRED)
Joined
Apr 3, 2004
Messages
61
Reaction score
0
Points
22
They have just driven the rover up to the rock to deploy the robotic arm, this should tell us exactly what it is made of. It definately is not part of the lander, you can see its been sitting on the surface for probably thousands of years, the wind has slowly sculpted dunes around it.

The latest pics from the rover have just been transmitted and they've positioned the rover to examine the object in the next few days:

http://qt.exploratorium.edu/mars/opport ... 14R0M1.JPG
 

Twin_Star

Gone But Not Forgotten
(ACCOUNT RETIRED)
Joined
Jul 23, 2003
Messages
811
Reaction score
16
Points
49
Well i'll be damned. They've found Beagle II :)
 

Mythopoeika

I am a meat popsicle
Joined
Sep 18, 2001
Messages
44,272
Reaction score
36,481
Points
309
Location
Inside a starship, watching puny humans from afar
TMS said:
Well i'll be damned. They've found Beagle II :)
You might be right.
 
A

Anonymous

Guest
LIFE ON MARS!!!!

http://www.space.com/scienceastronomy/mars_life_050216.html

Exclusive: NASA Researchers Claim Evidence of Present Life on Mars
By Brian Berger
Space News Staff Writer
posted: 16 February 2005
02:09 pm ET

WASHINGTON -- A pair of NASA scientists told a group of space officials at a private meeting here Sunday that they have found strong evidence that life may exist today on Mars, hidden away in caves and sustained by pockets of water.

The scientists, Carol Stoker and Larry Lemke of NASA’s Ames Research Center in Silicon Valley, told the group that they have submitted their findings to the journal Nature for publication in May, and their paper currently is being peer reviewed.

What Stoker and Lemke have found, according to several attendees of the private meeting, is not direct proof of life on Mars, but methane signatures and other signs of possible biological activity remarkably similar to those recently discovered in caves here on Earth.

Stoker and other researchers have long theorized that the Martian subsurface could harbor biological organisms that have developed unusual strategies for existing in extreme environments. That suspicion led Stoker and a team of U.S. and Spanish researchers in 2003 to southwestern Spain to search for subsurface life near the Rio Tinto river—so-called because of its reddish tint—the product of iron being dissolved in its highly acidic water.

Stoker did not respond to messages left Tuesday on her voice mail at Ames.

Stoker told SPACE.com in 2003, weeks before leading the expedition to southwestern Spain, that by studying the very acidic Rio Tinto, she and other scientists hoped to characterize the potential for a “chemical bioreactor” in the subsurface – an underground microbial ecosystem of sorts that might well control the chemistry of the surface environment.

Making such a discovery at Rio Tinto, Stoker said in 2003, would mean uncovering a new, previously uncharacterized metabolic strategy for living in the subsurface. “For that reason, the search for life in the Rio Tinto is a good analog for searching for life on Mars,” she said.

Stoker told her private audience Sunday evening that by comparing discoveries made at Rio Tinto with data collected by ground-based telescopes and orbiting spacecraft, including the European Space Agency’s Mars Express, she and Lemke have made a very a strong case that life exists below Mars’ surface.

The two scientists, according to sources at the Sunday meeting, based their case in part on Mars’ fluctuating methane signatures that could be a sign of an active underground biosphere and nearby surface concentrations of the sulfate jarosite, a mineral salt found on Earth in hot springs and other acidic bodies of water like Rio Tinto that have been found to harbor life despite their inhospitable environments.

One of NASA’s Mars Exploration Rovers, Opportunity, bolstered the case for water on Mars when it discovered jarosite and other mineral salts on a rocky outcropping in Merdiani Planum, the intrepid rover’s landing site chosen because scientists believe the area was once covered by salty sea.

Stoker and Lemke’s research could lead the search for Martian biology underground, where standing water would help account for the curious methane signatures the two have been analyzing.

“They are desperate to find out what could be producing the methane,” one attendee told Space News. “Their answer is drill, drill, drill.”

NASA has no firm plans for sending a drill-equipped lander to Mars, but the agency is planning to launch a powerful new rover in 2009 that could help shed additional light on Stoker and Lemke’s intriguing findings. Dubbed the Mars Science Laboratory, the nuclear-powered rover will range farther than any of its predecessors and will be carrying an advanced mass spectrometer to sniff out methane with greater sensitivity than any instrument flown to date.

In 1996 a team of NASA and Stanford University researchers created a stir when they published findings that meteorites recovered from the Allen Hills region of Antarctica contained evidence of possible past life on Mars. Those findings remain controversial, with many researchers unconvinced that those meteorites held even possible evidence that very primitive microbial life had once existed on Mars.
 
Last edited by a moderator:

ramonmercado

CyberPunk
Joined
Aug 19, 2003
Messages
52,219
Reaction score
27,797
Points
309
Location
Eblana
Space Observations Suggest Frozen Sea Under Mars' Surface

Space Observations Suggest Frozen Sea Under Mars' Surface

Did a series of volcanic eruptions cover an ancient sea on Mars, that to this day lies dormant as a frozen ocean?
Paris (AFP) Feb 21, 2005
A frozen sea surviving as blocks of pack ice may lie just beneath the surface of Mars, the New Scientist magazine said Monday citing observations from Europe's Mars Express spacecraft.
Images from the high resolution stereo camera on Mars Express showed of structures called plates that look similar to ice formations near Earth's poles.

These plates could indicate the first discovery of a large body of water beyond Mars' polar ice caps, the review said.

The team of researchers, led by John Murray of Britain's Open University, estimated the possible submerged ice sea at about 800 by 900 kilometresby 560 miles) in size and 45 metres (150 feet) deep on average.

The researchers said the evidence suggested that the plates, estimated to be about 5 million years old, were not just imprints left by ice that has now completely vanished.

While the site of the plates near Mars' equator means that sunlight should have melted any ice there, the team suggested that a layer of volcanic ash, perhaps a few centimetres thick, may protect the structures.

"I think it's fairly plausible," said Michael Carr, an expert on Martian water at the US Geological Survey in Menlo Park, California, who was not part of the team.

"Maybe the ice is still there in the ground, protected by a volcanic cover as they suggest," Carr said.

There is abundant evidence for the past presence of water on Mars but today the planet appears relatively dry, with ice confined to the planet's polar caps.

The discovery wwas to be presented Friday at the first Mars Express science conference in Noordwijk, the Netherlands.

In their paper the researchers traced a possible history for Mars' underground ice, saying it began with huge masses of ice floating in water that were later covered with volcanic ash, leaving the pack ice plates behind.

"If the reported hypothesis is true, then this would be a prime candidate landing site to search for possible extant life on Mars," said Brian Hynek, a research scientist at the Laboratory for Atmospheric and Space Physics at the University of Colorado at Boulder in the United States.

All rights reserved. © 2005 Agence France-Presse. Sections of the information displayed on this page (dispatches, photographs, logos) are protected by intellectual property rights owned by Agence France-Presse. As a consequence, you may not copy, reproduce, modify, transmit, publish, display or in any way commercially exploit any of the content of this section without the prior written consent of Agence France-Presse.

Related Links
MarsDaily
Search MarsDaily
Subscribe To MarsDaily Express

http://www.marsdaily.com/news/mars-wate ... e-05a.html
 

sunspot8

Gone But Not Forgotten
(ACCOUNT RETIRED)
Joined
Apr 3, 2004
Messages
61
Reaction score
0
Points
22
http://www.jpl.nasa.gov/missions/mer/images.cfm?id=1682

http://www.jpl.nasa.gov/images/mer/2005 ... 22-ani.mov

A dust devil spins across the surface of Gusev Crater just before noon on Mars. NASA's Spirit rover took the series of images in this spectacular 21-frame animation with its navigation camera on the rover's martian day, or sol, 486 (May 15, 2005).

The event occurred during a period of 9 minutes and 35 seconds beginning at 11:48 a.m. local Mars time, recording the dust devil's progress in a northeasterly direction about 1.0 kilometer (0.62 mile) away from Spirit's perch on the slopes of the "Columbia Hills." The whirlwind was traveling at about 4.8 meters per second (16 feet per second) and covered a distance of about 1.6 kilometers (1 mile).

Contrast has been enhanced for anything in the images that changes from frame to frame, that is, for the dust devil. The dust devil is about 34 meters (112 feet) in diameter.
 

James_H

And I like to roam the land
Joined
May 18, 2002
Messages
7,735
Reaction score
6,401
Points
309
that's very clear actually. Thanks
 

Timble2

Imaginary Person
Joined
Feb 9, 2003
Messages
5,948
Reaction score
2,136
Points
234
Location
In a Liminal Zone
That's fantastistic!

But how long before someone claims that it's MORE than just a Dust Devil?
 

GNC

King-Sized Canary
Joined
Aug 25, 2001
Messages
32,135
Reaction score
19,477
Points
309
A Martian Tasmanian Devil, perhaps?
 

sunspot8

Gone But Not Forgotten
(ACCOUNT RETIRED)
Joined
Apr 3, 2004
Messages
61
Reaction score
0
Points
22
In the last couple of months they've captured dozens and dozens of these dust devils....that one is particularly striking.
 
A

Anonymous

Guest
If you saw the BBC production 'Space Odyssey' you will have seen a simulation of an astronaut caught in such a dust devil; the fictional astronaut could barely feel it.

These eddies are occuring in a very very thin atmosphere; they are strong enough to lift the bone-dry dust, but not stromg enough to do noticeable damage.
 

sunspot8

Gone But Not Forgotten
(ACCOUNT RETIRED)
Joined
Apr 3, 2004
Messages
61
Reaction score
0
Points
22

Rubyait

Gone But Not Forgotten
(ACCOUNT RETIRED)
Joined
Sep 10, 2004
Messages
1,187
Reaction score
8
Points
54
Cold, dry and lifeless - a new take on Mars



New research on a green mineral that degrades easily in water and is present over much of the Martian surface is fuelling debates over the history of water and the current existence of life on the Red planet.

One study reveals that a region rich in the mineral olivine - which suggests it is has been "dry" for about 3 billion years - is actually four times larger than previously thought. That adds to a growing body of evidence suggesting Mars was mostly cold and dry - and not warm and wet - in the past.

The second study asserts that subsurface reactions of olivine and water could produce enough methane to account for recent observations of the gas in the atmosphere, removing the need to invoke living microbes to do the job.

Olivine forms at very high temperatures and is one of the first minerals to crystallise out of molten rock. But at lower temperatures and in the presence of water, it is thermodynamically "unhappy and breaks down really quickly into other minerals", says Phil Christensen, a geologist at Arizona State University in Tempe, US.

He and colleague Victoria Hamilton of the University of Hawaii in Honolulu, US, have used infrared images taken with NASA's Mars Odyssey spacecraft to show that the olivine-rich rocks on the flank of the volcano Syrtis Major cover a surface area of 113,000 square kilometres - about half the size of the UK.

Higher resolution
That is nearly four times larger than the estimate made by NASA's Mars Global Surveyor (MGS) spacecraft. The difference has been attributed to Odyssey's ability to resolve details as small as 100 metres across, a 30-fold improvement over MGS. Christensen and Hamilton’s study is published in the journal Geology (vol 33, p 433).

The rocks, at a latitude of 20° north of the planet's equator, appear to have formed through successive lava eruptions about 3 billion years ago. "To keep olivine around so long suggests this area of Mars may not have seen a lot of water or a warm climate," Hamilton told New Scientist.

That finding differs markedly from the recent discoveries made by the Mars rovers of minerals that form in the presence of water. But Christensen says such discoveries represent rare flooding events lasting for weeks or months and that for most of the planet's 4.5 billion-year history, any water has been locked in ice.

"I am not a proponent of the idea that Mars had oceans in the past," says Christensen. He says mineral mapping from orbit reveals most of the planet is covered in volcanic rocks, which "shows most of Mars hasn't seen much water". Scientists have failed to find minerals such as carbonates and clays that form in oceans on Earth, he says.

"I'm moving in the direction of 'cold and dry' more and more," agrees Hamilton. "But there are other scientists headed in the other direction, thinking Mars was warmer and wetter. It is an ongoing discussion."

Making methane
The discovery of more olivine on the surface of Mars also supports the argument that underground reserves of the mineral could produce methane, says geologist Mukul Sharma of Dartmouth College in Hanover, New Hampshire, US. He and colleague Chris Oze detail their proposal in the journal Geophysical Research Letters (vol 32, L10203).

Olivine tends to sink when it crystallises from magma, which "implies at some depth there has to be a lot more olivine than you see on the surface," says Sharma. The team says there is enough olivine in the top 10 kilometres of the crust to explain the recent detections of methane in Mars's atmosphere - if there are stores of liquid water underground, as many scientists suspect.

Water reacts with a common, iron-rich form of olivine by producing hydrogen gas, which then combines with carbon dioxide to produce methane. The gas could then leak to the surface through gullies.

"The easiest way to produce all the methane people have observed is by the reaction of olivine with water," Sharma told New Scientist. Other researchers have proposed that microbes might be a continuous source of the gas, which is easily destroyed by sunlight in the atmosphere.

http://www.newscientist.com/article.ns?id=dn7463
 

Rubyait

Gone But Not Forgotten
(ACCOUNT RETIRED)
Joined
Sep 10, 2004
Messages
1,187
Reaction score
8
Points
54
Researchers found that only a tiny fraction of the argon that was originally produced in the meteorite samples had been lost through the aeons, suggesting that the Martian surface has been in deep-freeze for most of the last four billion years.

'Four-billion-year chill' on Mars


A chemical study of Martian meteorites implies that the planet has always been cold and was rarely above freezing.

Writing in Science, US researchers say they are able to determine the maximum temperature the rocks experienced.

There is no evidence they were ever warm, the team says, as the meteorites would have recorded near-surface conditions for four billion years.

The water erosional features seen on Mars must have been made during very brief periods, they conclude.

Thermal history

Although the current average temperature at the Martian equator is about minus 55 Celsius, many scientists believe that the Red Planet was once warm enough for liquid water to have existed on its surface, and for life to possibly have evolved.

There is plentiful evidence that water has flowed on the surface. This includes the presence of deep canyons, dried up river beds and many examples of deposits left behind by running water.

But the recent analysis, by David Shuster of the California Institute of Technology, and Benjamin Weiss, of the Berkeley Geochronology Center, of meteorites blasted off the surface of Mars to Earth seems to paint a different picture.

The new work involves two of the seven known "nakhlite" meteorites (named after El Nakhla, Egypt, where the first such meteorite was found), and the celebrated ALH84001 meteorite that some scientists believe shows evidence of past microbial activity on Mars.

Using geochemical analysis techniques, the researchers reconstructed a "thermal history" for each of the meteorites to estimate the maximum long-term average temperatures to which they were subjected.

"We looked at meteorites in two ways," says Weiss. "First, we evaluated what the meteorites could have experienced during ejection from Mars, 11 to 15 million years ago."

Their conclusions were that ALH84001 could never have been heated to a temperature higher than 350 Celsius for even a brief period of time during the last 15 million years.

The nakhlites, which also show very little evidence of shock-damage, were unlikely to have been above the boiling point of water during their ejection from Mars 11 million years ago.

'Leaking' Argon

The other part of the research addressed the long-term thermal history of the rocks while they resided on Mars. The scientists did this by estimating the total amount of argon still remaining in the samples.

The gas argon is present in the meteorites as well as in many rocks on Earth as a consequence of the radioactive decay of potassium. A noble gas, argon is not very chemically reactive, and because the decay rate is precisely known it can be used to date rocks.

However, argon is also known to leak out of rocks at a temperature-dependent rate. The cooler the rock has been, the more argon will have been retained.

The researchers found that only a tiny fraction of the argon that was originally produced in the meteorite samples had been lost through the aeons, suggesting that the Martian surface has been in deep-freeze for most of the last four billion years.

"The small amount of argon loss that has apparently taken place in these meteorites is remarkable. Any way we look at it, these rocks have been cold for a very long time," says Shuster.

"The ALH84001 meteorite, in fact, couldn't have been above freezing for more than a million years during the last 3.5 billion years of history."

Water, water, everywhere?

This new line of research is a puzzle given the contrary evidence of running water on Mars.

"Our research doesn't mean that there weren't pockets of isolated water in geothermal springs for long periods of time, but suggests instead that there haven't been large areas of free-standing water for four billion years," says Shuster.

"Our results seem to imply that surface features indicating the presence and flow of liquid water formed over relatively short time periods."

In fact, the evidence shows that during the last four billion years, Mars has likely never been sufficiently warm for liquid water to have flowed on the surface for extended periods of time.

This implies that Mars has probably never had a hospitable environment for life to have evolved, unless biology got started during the first half-billion years of its existence, when the planet was probably warmer.

The study is bound to be controversial showing a disparity between those scientists who look at pictures of Mars to discern its history and those who study the only pieces of the planet we can examine in detail in the laboratory.

http://news.bbc.co.uk/1/hi/sci/tech/4703055.stm
 
Top