Posted on 06/19/2008 6:53:14 PM PDT by LibWhacker
Mars seasonal ice caps are entirely dry ice that is about 1 meter thick
Even an 8” (diameter) cassegrain scope will show the ice caps under good conditions (clear skies, near perihelion opposition, etc). If you want to see really nice detail then you need a 14”, but something in between would work pretty well. You can google images using keywords like amateur telescope mars (or jupiter, saturn, etc) to get some idea of what a scope can show. Most people say what size scope they used when doing photography. Bear in mind that you are usually seeing ideal pictures and not what is typical. Observing with a telescope takes a lot of patience and luck getting good viewing conditions.
"At that temperature and pressure the sublimation rate of water ice should be imperceptible."
As for me, the more I think about it, the more implausible it seems that centimeter size chunks of water ice could vanish by sublimation in 4 days in that trench. It doesn't take much reinforcement ( as per this citation ) to bolster my confidence.
http://www.lpi.usra.edu/meetings/polar2006/pdf/8031.pdf
Low temp, low pressure, the less chance of finding liquid water. Solid H2O will sublimate more readily on Mars due to low pressure. I can think of a number of ways in which that ice on Mars not only formed initially, but is now sublimating.
Other bodies in the solar system with probable H2O ice also have other conditions that vary greatly from those on Mars.
Has anyone seen Tourist Guy and/or Looter Guy?
What would be surprising is if there were NOT some form of H2O on mars.
Note mean conditions on Mars, Earth, and Venus are marked by the blue M,E, and V.
My understanding is that the solid/vapor line represents the vapor pressure of ice as a function of temperature, so we can read that the vapor pressure of ice at the mean Mars temperature of ~220K is ~1Pa, about 1/1000 the ambient pressure of 1kPa.
I can't say how this translates into a RATE of sublimation, and I haven't been able to find anything on the internet. You'd think there would be some kind of graph or something.
Not vaporized. Sublimated.
http://www.marsdaily.com/reports/Mars_Science_Is_A_Sublime_Affair_For_Phoenix_Lander_999.html
Mars Science Is A Sublime Affair For Phoenix Lander
Tucson AZ (JPL) Jun 20, 2008
Dice-size crumbs of bright material have vanished from inside a trench where they were photographed by NASA’s Phoenix Mars Lander four days ago, convincing scientists that the material was frozen water that vaporized after digging exposed it. “It must be ice,” said Phoenix Principal Investigator Peter Smith of the University of Arizona, Tucson. “These little clumps completely disappearing over the course of a few days, that is perfect evidence that it’s ice. There had been some question whether the bright material was salt. Salt can’t do that.”
The chunks were left at the bottom of a trench informally called “Dodo-Goldilocks” when Phoenix’s Robotic Arm enlarged that trench on June 15, during the 20th Martian day, or sol, since landing. Several were gone when Phoenix looked at the trench early today, on Sol 24.
Also early today, digging in a different trench, the Robotic Arm connected with a hard surface that has scientists excited about the prospect of next uncovering an icy layer.
The Phoenix science team spent Thursday analyzing new images and data successfully returned from the lander earlier in the day. Studying the initial findings from the new “Snow White 2” trench, located to the right of “Snow White 1,” Ray Arvidson of Washington University in St. Louis, co-investigator for the robotic arm, said, “We have dug a trench and uncovered a hard layer at the same depth as the ice layer in our other trench.”
On Sol 24, Phoenix extended the first trench in the middle of a polygon at the “Wonderland” site. While digging, the Robotic Arm came upon a firm layer, and after three attempts to dig further, the arm went into a holding position. Such an action is expected when the Robotic Arm comes upon a hard surface.
Meanwhile, the spacecraft team at Lockheed Martin Space Systems in Denver is preparing a software patch to send to Phoenix in a few days so scientific data can again be saved onboard overnight when needed. Because of a large amount a duplicative file-maintenance data generated by the spacecraft Tuesday, the team is taking the precaution of not storing science data in Phoenix’s flash memory, and instead downlinking it at the end of every day, until the conditions that produced those duplicative data files are corrected.
“We now understand what happened, and we can fix it with a software patch,” said Phoenix Project Manager Barry Goldstein of NASA’s Jet Propulsion Laboratory, Pasadena.
“Our three-month schedule has 30 days of margin for contingencies like this, and we have used only one contingency day out of 24 sols. The mission is well ahead of schedule. We are making excellent progress toward full mission success.”
The trench is an inch deep. Finding ice in the first inch is somewhat interesting, but water and ice have been known on Mars for a decade.
I am glad to know that I am not the only skeptic here. I am always lamblasted for being skeptical of crap like this...NASA would NEED too find something or else their funding would be jeopardy......someone correct me if I’m wrong...
and I am no chemist, by far, but how DOES ice (assuming it’s not dry ice) not melt or evaporate before our rover finds it? And why didn’t it just melt?? Wouldn’t it have to be REALLY hot for it to just evaporate??? Someone please enlighten me...
Remember that the air pressure on Mars is much lower than on Earth. Water ice will sublimate (evaporate) if the pressure and temperature are right.
Hydrogen is THE most abundant element in the universe, and oxygen is the THIRD most abundant.
What would be surprising is if there were NOT some form of H2O on mars.
H20 and CO2 (i.e. dry ice when solid) can sublimate directly from solid phase to vapor phase when the pressure is low enough.
At Earth’s average atmospheric pressure (~1 atm), the pressure is low enough for CO2 to do this, but not H20. In fact, CO2 requires over 5 atm pressure to form as a liquid.
At Mars’ pressure, the pressure is low enough for H20 to sublimate (or at least, to only be liquid at an extremely narrow temperature range somewhere in the range of 5 deg. Celsius). That is to say, whereas on earth water boils at 100 Celsius, on Mars, its boiling point is around 5 deg. Celsius. Not hot at all.
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