RE: [asa] Thinking about the age of Mars craters

Hi Bill,

I've recieved both arguments quite a few times especially the second. I first point out that although that is certainly a good question to ask it doesn't explain away that actual facts that the gasses in the rocks and those of the atmostphhere of Mars are in remarkable agreement. As mindboggling as it may seem to some that a rock could be thrown off the surface of Mars and then land on Earth (not just a single rock either, there are over 10 rocks identified a martial meteorites and that obviously has to be an extreme underestimate of the number of meteorites that have fallen even in modern times not to mention over the past millions of years) to just believe they can't come from Mars leaves the data that suggests they are as much of a mystery. I am thinking of giving out an anoymous questionaire this year asking what the students opinoins are about the rocks after the lectures. I supect that many will just take the first approach and say there is evidence for and against and so they will just stay in their comfort zone and say that they can't believe the rocks are from Mars. I really think that this ia what happens with many lay Christians and YEC. It doesn't matter how strong the evidence is for an old earth (or at least that YEC is wrong) the whole thing is just too overwhelming to allow one's mind to start contemplating that the earth may be old and becuase there seems to be pro and con evidence the default view will remain valid.

Joel

 
Thanks, Joel. Your answer is pretty much what I expected, but it's good to hear
it from someone who actually has read the literature. I suppose a YEC when
faced with the required millions of years for transit time might argue that
1) Then the rocks can't be from Mars
2) Since the comparison with atmospheric gases is done with the gases present
in Mars' atmosphere in the 70's, how can you identify them with the gases
present in Mars' atmosphere millions of years ago (assuming Mars existed
millions of years ago)?
Anyway, I think you've put together a quite valuable series of lessons to make
it clear to students the value of correlating many research results.

--- "Duff,Robert Joel" <rjduff@uakron.edu> wrote:

> Hi Bill,
> It really is a fascinating but somewhat complex story. I use a simplified
> version in my class whereby I first show many meteorites (mostly pictres from
> eBay) and ask them to make observations about the rocks. I then ask them to
> list some features of meteorites. After some debate about whether they have
> any common properties (usually no one can agree to any particular feature
> that makes them meteorites) eventually I ask the question, But how can you
> know that these rocks aren't just rocks from the earth? After the usuall
> pregnant pause (maybe someone will say that the rocks were seen falling from
> the sky) I then show pictures of researchers looking for meteorites in
> Antartica and we debelop hypotheses about how rocks could have gotten to
> these remote locations on barren ice fields. Usually by the end of the first
> lecture I've convinced them that the best hypothesis is that the rocks fell
> from "the heavens". We also talk about radiometric ages of the rocks, cosmic
> ray effects on rock composition and a few other features of typical
> meteorites. I then ask the question, but this supposed evidence of life on
> Mars was found in a rock, does anyone remember a mission to Mars to retrieve
> martian rocks? No one can remember and so I show the ALH84001 rock found in
> antarctica and say well here is rock from Mars. Do you believe this rock is
> from Mars? (usually several people wills say they can't believe it). I tell
> them at this point that my goal for the next lecture is to at least convince
> them that this rock was likely on Mars at some point in the past. To do so I
> go into a little intro into chemistry, which I have to do anyway in this
> general class, and we talk about elements and molecules and then I show the
> distrubution of elements in the universe, on earth and in living things. We
> also talk a little bit about isotopes. I then talk about rock formation and
> how gasseous molecules get trapped inside the rock when it crystalizes. We
> talk about how rocks, like this meteorite, can be melted and those gasses
> released and how they can be very precisely measured. Those gasses then
> represent the gasses present in the atmostpher as when the rock crystalized.
> Now I pull out my climatic graphic: the graph which compares the percentage
> of different molecules/elements in the atmosphere of Mars today and the
> gasses found deep inside the ALH84001 meteorite. I also show the percentage
> of those same elemenst/molecules in the earth's atmosphere. What is very
> clear is an amazing correlation of the gasses in the meteorite and the gasses
> on Mars as opposed to the gasses on earth. I further point out even the
> ratios of some isotopes are the same between the two. At this point I
> usually ask how we know what the gasses of Mars atmosphere are and several
> students will talk about the current probes there but actually we knew about
> the composition of the Mars atmospher all the way back into the late 70s when
> the Viking I and II landed on Mars and took measurements. It was because of
> these measurements that Mars meteorites were identified on earth before the
> current wave of Mars landers and orbiters arrived. The last topic I addres
> in my question is to pose the question, even if you can understand the
> argument for these rocks as having their origin on Mars you must still have
> another question answered for you to actually believe they came from Mars.
> What would that question be? Usually one student will finally ask "How did
> that rock get to earth?" Then I ask them to come up with hypotheses and we
> eventually figure out that asteroid impacts could have knocked rocks right
> off the surface of Mars into space. It still sounds unbelievabel to many but
> I try to show a few stats about the predictons of number of Mars space rocks
> and how statistics actually suggests that rather than unlikely it is very
> likely that rocks from Marss have migrated to earth. Of course this is the
> first inkling in the class for many that in order for this to be likely you
> need millions of years for the rocks to wander through space and have a
> chance to hit earth. I don't ask this question in my class but one could
> easily ask the YEC how to explain Mars rocks today. The statistics won't
> work in their favor having only a short time for rocks to make there way that
> distance.
>
> I use the presence of the knowledge of the atmosphere in the late 70s as an
> example of how we use data gathered in basic science that may seem somewhat
> inconsequential at the time to make discoveries about other things many years
> later. Without that atmospheric data it would have been much more difficult
> (possibly not possible yet unless there are other clear signatures of Mars
> meteorites I don't know about) to have identified these meteorites and been
> able to study Mars geology right here on earth.
>
> Joel
>
>
>
> --- "Duff,Robert Joel" <rjduff@uakron.edu> wrote:
>
> > [snip] In that class we look at Mars meteorites on
> > earth as a way to talk bout chemistry (showing the gases in the rocks are
> > similar to gases found on Mars) and various aspects of the scientific
> > process.
> >
> One question I have about the Mars meteorites is how we know they originated
> on Mars.
>
> Bill Hamilton
> William E. Hamilton, Jr., Ph.D.
> 248.652.4148 (home) 248.821.8156 (mobile)
> "...If God is for us, who is against us?" Rom 8:31
>
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Bill Hamilton
William E. Hamilton, Jr., Ph.D.
248.652.4148 (home) 248.821.8156 (mobile)
"...If God is for us, who is against us?" Rom 8:31

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Received on Thu Aug 10 11:37:47 2006