Doubts about ALH84001

Palomar · 2004-05-05 10:32:53

http://www.spaceref.com/news/viewpr.html?pid=14162]1996 NASA "evidence" in question

*I would summarize a bit of what I've read, as I usually do, but something's going on with my computer.

--Cindy

bolbuyk · 2004-05-13 07:17:59

These doubts were there from the beginning. I never thought ALH84001 contained fossils or was even Martian.

1. How can Martian vulcanic rock be 'launched' in space?

2. How can one accordance the PAC's in ALH84001 with the absence of it on Mars, according to Vikings gas-analysator?

3. Structures seem to be to small to suggest bacterians, because they couldn't contain the organels.

4. How can you definitely exclude earth-life contamination?

smerral · 2004-05-14 12:23:46

I don't think there is much doubt that the meteorite came from Mars. In fact the latest finding that Bounce rock is closely related to other meteorites helps seal the case for rock transfers between Mars and Earth. There has been a lot of work done on this. The fact that the microbes are small is a problem though. However, other meteorites are being studied which look even more intriguing than AL, including the Shergotty meterorite, which has so much in common with Bounce:

http://www.planetary.org/news/articlear … ...99.html

The jury is still out.

lunarmark · 2004-05-27 03:38:12

As an extensive collector and Studier of meteorites myself, I can tell you these Martian meteorites are from mars without question, recent evidence from the Mars Rovers also backs this up, but it was pretty certain before then anyhow. here's why...

The Martian meteorites are subdivided essentially into three groups Shergottites, Nakhalites, Chassignites. These are all Basaltic (or cumulative Basaltic) rocks, which differ completley to all the other meteorite types, so they clearly belong to a seperate parent body, than all the other falls.

Next the Isotopic Ratio's match Mars rock studied directly by space probes exactly (different elemental ratios exsist depending on the parent body, i.e each one has its own unique signiture), Gases trapped in the rock, match the Martian atmosphere. Orbital back calculations from witnessed Martian meteorite falls suggest martian origin. Dating of the rocks by radioisotope decay, dates them far too young to be from asteroids, which all stopped being volcanic billions of years ago due to their small size) Now we have direct observational and isotopic evidence from the Mars Rovers that indicate the Bounce rock is a Shergottite type rock.

Lastly the mechanism that ejects rock from the surface of mars is actually quite straight forward, a meteor striking the surface at a certain critical angle can easily eject debris into martian orbit (and beyond) this has been studied by many people, and just as rock (meteorite) has reached earth from the moon, so to has it reached us from mars. Earth and Venus have thick atmosphere and higher gravity so its less liklely that rock from these planets would escape but still not impossible.

There are few things in science that we can be certain of, but given this amount of evidence, its looking pretty good!

:band:

dicktice · 2004-05-27 07:26:04

But . . . did you find any blueberries? :hm:

lunarmark · 2004-05-27 07:43:26

Some Blueberries would be nice ! - but Because most of the ejected Martian material was essentially 'smashed up' and parlty melted (due to the original energy of the meteor's impact, i.e essentially a Breccia) details like Blueberries would lilkley not survive.

In any case most of the Martian meteorites represent samples from deeper down rather than the actual sub soil. Although we do have 'compacted soil meteorites' from the asteroids, this class of meteorite is known as a 'Howardite'.

Interestingly there are no Martian Sedimentry rocks represented in meteorites, (i.e layered by water or volcanic ash deposition) so one can only assume this type of rock is extreemly friable and wouldn't survive ejection or entry into our atmosphere since it would vaporise very easily.

Shaun Barrett · 2004-05-27 19:53:48

Hi Bolbuyk!
I believe your doubts about impact transfer of material between Earth and Mars must surely have been laid to rest by the answers provided here.

In response to your question about Polycyclic Aromatic Hydrocarbons (PAHs) found in ALH 84001, and other points you raise:-

1) The Gas Chromatograph Mass Spectrometer used on the Viking missions has been found to be too insensitive even to detect breeding colonies of bacteria in Antartic soils! Its results on Mars must therefore be discounted.

2) If the PAHs found inside ALH84001 were the result of terrestrial contamination, chemicals seeping in from outside while sitting on the Antarctic ice, one would expect to find a negative concentration gradient as one analysed material deeper into the meteorite, i.e. a higher concentration of PAHs on the outside and lower concentrations towards the centre.
On the contrary, the PAHs are more concentrated in the interior, which indicates they were in the rock before it left Mars.

3) The small size of the purported bacteria in ALH84001 has been a show-stopper for many researchers, who argue, as you do, that the volume of these structures is simply too small to contain even the most basic of the molecular mechanisms essential to life.
A controversial hypothesis involving so-called nanobacteria has been used as a counter-argument that life can in fact exist at very small scales; scales hitherto dismissed as impossible. It remains to be seen whether this hypothesis ever becomes mainstream.
However, the nanobacteria hypothesis mightn't be necessary to explain the 'micro-fossils' in ALH84001. It has been found that bacteria subjected to extreme privation tend to shrink and shrivel as they sink towards death. There could surely be many possible scenarios in which the ALH84001 bacteria, if indeed they were bacteria, suffered a lack of nutrition and/or water before they died. If so, one would expect their remains to be much smaller than a living bacterium.

4) One more piece of evidence in favour of the micro-fossil hypothesis is the existence of the tiny perfectly-formed magnetite crystals found in association with the 'bacterial' remains. As you know, these are typical of crystals found in terrestrial magnetotactic bacteria, which use the magnetite to orientate themselves in dark murky water.
I think this is a particularly compelling piece of additional evidence that we may indeed be dealing with the remains of martian bacteria in the Allan Hills meteorite.
(You may want to have a look at http://science.nasa.gov/headlines/y2000 … 1.htm]this site, which gives a neat summary of the magnetite evidence. Be sure to click on 'side-

bolbuyk · 2004-05-28 07:29:42

Interesting stuff, also the magnetism on Mars which is required to hold the hypothesis.

Mars_B4_Moon · 2023-05-10 12:06:36

an old thread worth a bump with news

The mysterious origins of Martian meteorites
https://www.marsdaily.com/reports/The_m … s_999.html

In August 1865, a 10-pound rock fell from space to Earth, landing with a bang in the remote village of Sherghati, India. After being recovered by witnesses to the event, the stone passed into the possession of a local British magistrate who endeavored to identify the source of the strange object. After more than a century of studying the meteorite fragments-so-called shergottites-researchers in the 1980s finally determined its alien origins: our neighboring planet, Mars.

Until humans are able to bring back samples from Mars, the only pieces of the Red Planet found on Earth are Martian meteorites such as the shergottites. The journey for these little Martian travelers has been violent: for Mars rocks to get to Earth, they must have been ejected from the Red Planet's surface with enough force to escape Martian gravity. This ejection was likely due to a large impact on Mars. The rocks withstood the massive temperatures and pressures of this impact and flew through the vacuum of space, eventually crash-landing on our own planet.

For decades, scientists have worked on modeling the kind of Martian impact events that send bits of the Red Planet to Earth. Now, researchers at Caltech and the Jet Propulsion Laboratory (JPL), which Caltech manages for NASA, have conducted experiments to simulate the so-called "shock pressure" experienced by Martian rocks. They have found that the pressure required to launch a rock from Mars into space is much lower than originally thought.

The research was conducted in the laboratory of Paul Asimow (MS '93, PhD '97), the Eleanor and John R. McMillan Professor of Geology and Geochemistry. The study is described in a paper appearing in the journal Science Advances on May 3 and is a collaboration with JPL.

Meteorites from varied sources have been discovered on Earth for millennia, but their origins were not known until much more recently. As NASA's Viking orbiters made measurements of Mars's atmospheric composition in the late 1970s, Caltech's Ed Stolper (now the Judge Shirley Hufstedler Professor of Geology) was one of the first to suggest that shergottites are from Mars-confirmed later when gases in the thin Martian atmosphere matched up with the gases encapsulated in the meteorites.

But that is not all a meteorite's composition can tell us about its journey. One major component of Martian rocks is the crystalline mineral plagioclase. Under high pressures, such as an intense impact, plagioclase transforms into the glassy material known as maskelynite. Finding maskelynite in a rock, therefore, indicates the types of pressure the sample came into contact with. In the last five years, Martian meteorites have been discovered with a blend of both plagioclase and maskelynite, indicating an upper bound for the pressures they were subjected to.

In the new study, led by Caltech staff scientist Jinping Hu, the team conducted experiments to smash plagioclase-containing rocks from Earth and observe how the mineral transforms under pressure. The team developed a more accurate method to simulate Martian impacts in shock-recovery experiments, utilizing a powerful "gun" to blast rocks with projectiles traveling over five times the speed of sound. Previous shock-pressure experiments required reverberating shock waves through a steel chamber, which gives an inaccurate picture of what happens during an impact event on Mars.

"We're not on Mars, so we can't watch a meteorite strike in person," says Yang Liu, a planetary scientist at JPL and a co-author on the study. "But we can recreate a similar kind of impact in a lab setting. By doing so, we found it takes much less pressure to launch a Mars meteorite than we thought."

Previous experiments had shown that plagioclase turns into maskelynite at a shock pressure of 30 gigapascals (GPa), which is 300,000 times the atmospheric pressure one experiences at sea level, or 1,000 times the pressure a submersible comes into contact with while diving beneath 3 kilometers of ocean water. This new study shows that the transition actually happens at around 20 GPa-a significant difference from previous experiments. In particular, the new pressure threshold is consistent with evidence from other high-pressure minerals in these meteorites indicating that their shock pressures must have been less than 30 GPa. Nine out of the 10 high-pressure minerals found in Martian meteorites were discovered at Caltech in studies led by mineralogist Chi Ma, Caltech's director of analytical facilities, and a co-author of the study.

"It has been a significant challenge to model an impact that can launch intact rocks from Mars while shocking them to 30 GPa," Asimow says. "In this context, the difference between 30 GPa and 20 GPa is significant. The more accurately we can characterize the shock pressures experienced by a meteorite, the more likely it becomes that we can identify the impact crater on Mars from which it originated."

The paper is titled "Shock-recovered maskelynite indicates low-pressure ejection of shergottites from Mars." Hu, Asimow, Liu, and Ma are co-authors. Funding was provided by NASA, Caltech-JPL, and the National Science Foundation.

tahanson43206 · 2023-05-10 12:30:47

For Mars_B4_Moon re #9

Thanks for bringing Palomar's topic back to life, and for providing the excerpt from the link!

The discovery that we humans might be able to match meteorites found on Earth to the source craters on Mars is quite surprising (to me for sure!)

(th)

Mars_B4_Moon · 2024-03-01 06:55:07

Study reveals potential for life's building blocks from Mars' ancient atmosphere

https://www.spacedaily.com/reports/Stud … e_999.html

Mars_B4_Moon · 2024-04-05 16:36:56

Mars May Not Have Had Liquid Water Long Enough For Life To Form

https://arstechnica.com/science/2024/04 … e-to-form/

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#1 2004-05-05 10:32:53

Re: Doubts about ALH84001

#2 2004-05-13 07:17:59

Re: Doubts about ALH84001

#3 2004-05-14 12:23:46

Re: Doubts about ALH84001

#4 2004-05-27 03:38:12

Re: Doubts about ALH84001

#5 2004-05-27 07:26:04

Re: Doubts about ALH84001

#6 2004-05-27 07:43:26

Re: Doubts about ALH84001

#7 2004-05-27 19:53:48

Re: Doubts about ALH84001

#8 2004-05-28 07:29:42

Re: Doubts about ALH84001

#9 2023-05-10 12:06:36

Re: Doubts about ALH84001

#10 2023-05-10 12:30:47

Re: Doubts about ALH84001

#11 2024-03-01 06:55:07

Re: Doubts about ALH84001

#12 2024-04-05 16:36:56

Re: Doubts about ALH84001

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