[meteorite-list] Pebbly Rocks Testify to Old Streambed on Mars (MSL)

From: lebofsky at lpl.arizona.edu <lebofsky_at_meteoritecentral.com>
Date: Sat, 1 Jun 2013 05:14:15 -0700
Message-ID: <d13431f4ed99d9b7262fee7473588972.squirrel_at_webmail.lpl.arizona.edu>

Hi Steve:

Yes, I did see your video link. Thanks for sending that. All that this
demonstrates is that CO2 is denser than air and that, when it displaces
the oxygen, the candle goes out. So, even in this case it is not the force
of the CO2 that is putting the flame out, but the lack of oxygen.

CO2 gas is 1.5 as dense as air, but 1/500 the density of water. I doubt
that you could mimic the know effects of moving water in a stream bed with
a much less dense gas. If nothing else, the gas would disperse in the
atmosphere rapidly unlike the much denser water.

Sublimation is a very slow process, look at comet nuclei. There is a limit
to how fast something can sublimate. As the ice warms up and turns to gas,
the energy needed to do this actually cools the surface (the same thing as
evaporative cooling which cools you as sweat evaporates off of your skin).
I wrote several papers years ago on ice sublimation.

The scientists used the sizes and size distribution of the rounded grains
to compare with what we see in stream beds on Earth and can actually come
up with depth, duration, and speed of the water. I do not see how you
could replicate that with a gentle flow of gas no matter how long you had.

Your idea is interesting, but decades of research have shown that geologic
processes on Mars (and other objects) are not that different than what we
see on Earth. If we see on Mars what looks like a stream bed on Earth, it
is likely that the process that formed the stream bed on Earth (water)
also did this on Mars. So, what conditions would have been necessary for
the stream bed to have formed on Mars? A little more atmosphere and a
little warmer!

I hope that this helps.

Larry




> I believe I did not describe properly what I was trying to say. The video
> link I sent clearly showed co2 gas being poured from a beaker. During the
> cold mars night a thin layer of co2 frost can form on a hillside. when
> daylight returns and thaws the frost, the recently sublimated co2 being
> colder than the surrounding atmosphere is going to flow down hill.
> Millions of years of colder denser gas flowing down hill is going to cause
> erosion that simulates the flow of water.
> Mars has an 100 thousand year polar freeze thaw cycle. When billions
> of tons of co2 sublimate from the poles its going to flow out from the
> poles and cause erosion as it does so. Millions of years of this
> repeated cycle of the colder gas flowing down hill is going to carve
> what looks like river beds, canyons and lakes. all without any water
> needed.
> Cheers
> Steve
>
> --- On Fri, 5/31/13, Graham Ensor <graham.ensor at gmail.com> wrote:
>
>> From: Graham Ensor <graham.ensor at gmail.com>
>> Subject: Re: [meteorite-list] Pebbly Rocks Testify to Old Streambed on
>> Mars (MSL)
>> To: lebofsky at lpl.arizona.edu
>> Cc: "Steve Dunklee" <steve.dunklee at yahoo.com>, "Meteorite Mailing List"
>> <meteorite-list at meteoritecentral.com>, "Ron Baalke"
>> <baalke at zagami.jpl.nasa.gov>
>> Date: Friday, May 31, 2013, 11:39 PM
>> Hi Larry, that's exactly the word I
>> was trying to look
>> for..."sublimates"...just could not bring it to mind. (any
>> was being
>> too lazy to look it up)? So my thoughts were
>> right....very unlikely
>> for there ever to be any liquid CO2 on Mars.
>>
>> G
>>
>> On Fri, May 31, 2013 at 6:32 PM,? <lebofsky at lpl.arizona.edu>
>> wrote:
>> > Hi Graham and Steve:
>> >
>> > Technically, you are wrong--CO2 sublimates (turns from
>> solid to gas) and
>> > does not evaporate (turns from liquid to gas). The
>> triple point (where
>> > solid, liquid, and gas exist)of CO2 is 5.1 atmospheres.
>> Since the "sea
>> > level" pressure on Mars is about 0.006 atmospheres, the
>> atmospheric
>> > pressure on Mars would have had to have been 1000 times
>> greater than it is
>> > now. Not very likely. To have liquid water (enough for
>> flowing rivers) the
>> > pressure would have to be about 0.006 atmospheres at 0
>> degrees C. In fact,
>> > I think that this is how they originally defined the
>> mean surface of Mars.
>> > The only problem is that Mars is generally too cold at
>> this pressure for
>> > there to be liquid water, so you would need a warmer
>> Mars (by a about 60
>> > degrees centigrade for the "average" temperature) in
>> order to get water
>> > flowing on Mars. This is much more likely than a
>> 1000-fold increase in
>> > surface pressure.
>> >
>> > In fact, there is evidence for liquid water on Mars,
>> but not in great
>> > amounts (gullies, for example).
>> >
>> > Larry
>> >
>> >> Hi Steve,
>> >>
>> >> Liquid CO2 cannot exsist as a liquid at atmospheric
>> pressure. It must
>> >> be pressurized above 60.4 psi to remain as a
>> liquid....so would it
>> >> have ever flowed on Mars at all? Solid CO2
>> evaporates to gas on Earth
>> >> and I would say it does the same on
>> Mars....somebody correct me there
>> >> if I am wrong?
>> >>
>> >> Interesting thought about bog iron.....we would
>> have hopes on Mars
>> >> which would be the reverse of our hopes on Earth.
>> Many pieces of bog
>> >> iron have got folks excited on Earth because they
>> were thought to be
>> >> meteorites but are meteorwrongs. On Mars we would
>> be hoping that a
>> >> meteorite was bog iron as that would indicate a bog
>> and thus peat and
>> >> plantlife. As far as I know bog iron is associated
>> with pea bogs and
>> >> cannot form just with water...now a layer of old
>> peat bog/coal would
>> >> be an exciting find on Mars.
>> >>
>> >> Graham
>> >>
>> >> On Fri, May 31, 2013 at 9:41 AM, Steve Dunklee
>> <steve.dunklee at yahoo.com>
>> >> wrote:
>> >>> What is the composition of the pebbles? and
>> other deposits? if there are
>> >>> not carbonates or other water soluable
>> constiuentes then we may have to
>> >>> accept the flow of carbon dioxide as the cause
>> of the water like erosion
>> >>> caused by the heating and cooling? on
>> mars. where is the bog iron and
>> >>> limestone or other precipitates which would be
>> formed by water? As much
>> >>> as I would wish for life and water on mars I
>> see nothing to convince me
>> >>> yet.
>> >>> Cheers
>> >>> Steve Dunklee
>> >>> --- On Thu, 5/30/13, Ron Baalke <baalke at zagami.jpl.nasa.gov>
>> wrote:
>> >>>
>> >>>> From: Ron Baalke <baalke at zagami.jpl.nasa.gov>
>> >>>> Subject: [meteorite-list] Pebbly Rocks
>> Testify to Old Streambed on Mars
>> >>>> (MSL)
>> >>>> To: "Meteorite Mailing List" <meteorite-list at meteoritecentral.com>
>> >>>> Date: Thursday, May 30, 2013, 7:01 PM
>> >>>>
>> >>>> http://www.jpl.nasa.gov/news/news.php?release=2013-181
>> >>>>
>> >>>>
>> >>>> Pebbly Rocks Testify to Old Streambed on
>> Mars
>> >>>> Jet Propulsion Laboratory
>> >>>> May 30, 2013
>> >>>>
>> >>>> PASADENA, Calif. - Detailed analysis and
>> review have borne
>> >>>> out
>> >>>> researchers' initial interpretation of
>> pebble-containing
>> >>>> slabs that
>> >>>> NASA's Mars rover Curiosity investigated
>> last year: They are
>> >>>> part of an
>> >>>> ancient streambed.
>> >>>>
>> >>>> The rocks are the first ever found on Mars
>> that contain
>> >>>> streambed
>> >>>> gravels. The sizes and shapes of the
>> gravels embedded in
>> >>>> these
>> >>>> conglomerate rocks -- from the size of sand
>> particles to the
>> >>>> size of
>> >>>> golf balls -- enabled researchers to
>> calculate the depth and
>> >>>> speed of
>> >>>> the water that once flowed at this
>> location.
>> >>>>
>> >>>> "We completed more rigorous quantification
>> of the outcrops
>> >>>> to
>> >>>> characterize the size distribution and
>> roundness of the
>> >>>> pebbles and sand
>> >>>> that make up these conglomerates," said
>> Rebecca Williams of
>> >>>> the
>> >>>> Planetary Science Institute, Tucson, Ariz.,
>> lead author of a
>> >>>> report
>> >>>> about them in the journal Science this
>> week. "We ended up
>> >>>> with a
>> >>>> calculation in the same range as our
>> initial estimate last
>> >>>> fall. At a
>> >>>> minimum, the stream was flowing at a speed
>> equivalent to a
>> >>>> walking pace
>> >>>> -- a meter, or three feet, per second --
>> and it was
>> >>>> ankle-deep to
>> >>>> hip-deep."
>> >>>>
>> >>>> Three pavement-like rocks examined with the
>> telephoto
>> >>>> capability of
>> >>>> Curiosity's Mast Camera (Mastcam) during
>> the rover's first
>> >>>> 40 days on
>> >>>> Mars are the basis for the new report. One,
>> "Goulburn," is
>> >>>> immediately
>> >>>> adjacent to the rover's "Bradbury Landing"
>> touchdown site.
>> >>>> The other
>> >>>> two, "Link" and "Hottah," are about 165 and
>> 330 feet (50 and
>> >>>> 100 meters)
>> >>>> to the southeast. Researchers also used the
>> rover's
>> >>>> laser-shooting
>> >>>> Chemistry and Camera (ChemCam) instrument
>> to investigate the
>> >>>> Link rock.
>> >>>>
>> >>>> "These conglomerates look amazingly like
>> streambed deposits
>> >>>> on Earth,"
>> >>>> Williams said. "Most people are familiar
>> with rounded river
>> >>>> pebbles.
>> >>>> Maybe you've picked up a smoothed, round
>> rock to skip across
>> >>>> the water.
>> >>>> Seeing something so familiar on another
>> world is exciting
>> >>>> and also
>> >>>> gratifying."
>> >>>>
>> >>>> The larger pebbles are not distributed
>> evenly in the
>> >>>> conglomerate rocks.
>> >>>> In Hottah, researchers detected alternating
>> pebble-rich
>> >>>> layers and sand
>> >>>> layers. This is common in streambed
>> deposits on Earth and
>> >>>> provides
>> >>>> additional evidence for stream flow on
>> Mars. In addition,
>> >>>> many of the
>> >>>> pebbles are touching each other, a sign
>> that they rolled
>> >>>> along the bed
>> >>>> of a stream.
>> >>>>
>> >>>> "Our analysis of the amount of rounding of
>> the pebbles
>> >>>> provided further
>> >>>> information," said Sanjeev Gupta of
>> Imperial College,
>> >>>> London, a
>> >>>> co-author of the new report. "The rounding
>> indicates
>> >>>> sustained flow. It
>> >>>> occurs as pebbles hit each other multiple
>> times. This wasn't
>> >>>> a one-off
>> >>>> flow. It was sustained, certainly more than
>> weeks or months,
>> >>>> though we
>> >>>> can't say exactly how long."
>> >>>>
>> >>>> The stream carried the gravels at least a
>> few miles, or
>> >>>> kilometers, the
>> >>>> researchers estimated.
>> >>>>
>> >>>> The atmosphere of modern Mars is too thin
>> to make a
>> >>>> sustained stream
>> >>>> flow of water possible, though the planet
>> holds large
>> >>>> quantities of
>> >>>> water ice. Several types of evidence have
>> indicated that
>> >>>> ancient Mars
>> >>>> had diverse environments with liquid water.
>> However, none
>> >>>> but these
>> >>>> rocks found by Curiosity could provide the
>> type of stream
>> >>>> flow
>> >>>> information published this week.
>> Curiosity's images of
>> >>>> conglomerate
>> >>>> rocks indicate that atmospheric conditions
>> at Gale Crater
>> >>>> once enabled
>> >>>> the flow of liquid water on the Martian
>> surface.
>> >>>>
>> >>>> During a two-year prime mission,
>> researchers are using
>> >>>> Curiosity's 10
>> >>>> science instruments to assess the
>> environmental history in
>> >>>> Gale Crater
>> >>>> on Mars, where the rover has found evidence
>> of ancient
>> >>>> environmental
>> >>>> conditions favorable for microbial life.
>> >>>>
>> >>>> More information about Curiosity is online
>> at:
>> >>>> http://www.jpl.nasa.gov/msl , http://www.nasa.gov/msl and
>> >>>> http://mars.jpl.nasa.gov/msl/ .
>> >>>>
>> >>>> You can follow the mission on Facebook at:
>> >>>> http://www.facebook.com/marscuriosity and
>> >>>> on Twitter at
>> >>>> http://www.twitter.com/marscuriosity .
>> >>>>
>> >>>> Guy Webster 818-354-6278
>> >>>> Jet Propulsion Laboratory, Pasadena,
>> Calif.
>> >>>> guy.webster at jpl.nasa.gov
>> >>>>
>> >>>> 2013-181
>> >>>>
>> >>>>
>> ______________________________________________
>> >>>>
>> >>>> Visit the Archives at http://www.meteorite-list-archives.com
>> >>>> Meteorite-list mailing list
>> >>>> Meteorite-list at meteoritecentral.com
>> >>>> http://six.pairlist.net/mailman/listinfo/meteorite-list
>> >>>>
>> >>> ______________________________________________
>> >>>
>> >>> Visit the Archives at http://www.meteorite-list-archives.com
>> >>> Meteorite-list mailing list
>> >>> Meteorite-list at meteoritecentral.com
>> >>> http://six.pairlist.net/mailman/listinfo/meteorite-list
>> >> ______________________________________________
>> >>
>> >> Visit the Archives at http://www.meteorite-list-archives.com
>> >> Meteorite-list mailing list
>> >> Meteorite-list at meteoritecentral.com
>> >> http://six.pairlist.net/mailman/listinfo/meteorite-list
>> >>
>> >
>> >
>>
> ______________________________________________
>
> Visit the Archives at http://www.meteorite-list-archives.com
> Meteorite-list mailing list
> Meteorite-list at meteoritecentral.com
> http://six.pairlist.net/mailman/listinfo/meteorite-list
>
Received on Sat 01 Jun 2013 08:14:15 AM PDT