Starship Asterisk*

Sorry, been busy working on the boat.

The magnetic field of Venus is virtually nonexistent with only a few anomalous areas of readings. Here is one site that may help. http://www.nineplanets.org/venus.html

Venus is also only about 80% mass of earth and about 5% smaller than earth.

another is, http://image.gsfc.nasa.gov/poetry/venus/TransitFAQs.html

There was a program about Venus (NOVA?) and scientists trying to solve the many unanswered questions about the veiled planet.

It's assumed that the reason Venus has such a dense atmosphere is that it is being replenished by volcanoes...but so far there isn't any direct evidence of volcanic activity, ala Io or Triton.

Besides the magnetosphere argument, Mars is far less massive than Venus, so that's another reason it couldn't hold on to a dense atmosphere, even as cold as it is.

Craterchains, do you know of a site that has a comparison of the planet's relative magnetic field strengths?

As far as I know Mars' field is weak, if even existent. Mercury has a weak field as I recall, but I don't remember reading about the field of Venus. If I had to guess I would have assumed that Venus would have a similar field to the Earth since the two planets' mass and structure are similar (if I remember correctly, the current theory as to the source of Earth’s magnetic field is, in a nutshell, that electric current is created in the molten iron core because it is rotating faster than the outer solid sections of the Earth).

If you like math, calculate the escape velocities of Mars and Venus and then the kinetic energy of CO2 at the temperatures and pressures of both planets - you'll have your answer. For more fun, try it again with the molar mass of hydrogen.

OK, I'm learning way too much of the bad air in a place I'll never visit.

Carbon Dioxide is one of the heaviest gasses and its effect at the surface of Venus is cause for the greater density of the atmosphere.

Even so, with the weaker magnetic field offering very little protection from the stronger solar wind, I would assume the atmosphere is being leached of its higher altitudes, and at a faster rate than what Mars suffered.
If true then wouldn't the atmosphere need constant resupply?
With Venus being very hot and active I would assume volcanic activity to be the source of new CO2 supplies.

With all most no magnetic field, Venus has an atmosphere that is way denser than Earth's, about 90 times? Just an interesting point. Then compare the numbers to Mars and see what you think? Also it is teresting that Mars showed a different atmosphere than that now showing from the earlier landers and today's landers. Peculiar and highly intriguing to me.

What "looks like" is kind of fun at times a sure breaks up some horrible monotonous stints at planetary research at times when one stumbles across such things as the LBJ like B&W image. :o

[quote="craterchains"]The face that kind of looks like LBJ ! ? ! ? :shock: [/quote]
Yes !! I was thinking an old Black & White TV; but LBJ is right on.

[quote="craterchains"]For those that think Mars lost it's atmosphere due to a "solar wind", you should check out Venus's magnetic field.[/quote]
Ow!! I read [url=http://www-ssc.igpp.ucla.edu/personnel/russell/papers/venus_mag/][color=blue][u]this page[/u][/color][/url] and now know much more than I ever needed about Venus' magnetic field.

But I don't understand your argument as [url=http://zebu.uoregon.edu/~soper/Venus/atmosphere.html][color=blue][u]venus' atmosphere[/u][/color][/url] seems to have lost most of its water vapor and lighter gasses which is consistant with the weak magnetic field.

http://asterisk.apod.com/viewtopic.php?t=605 (old)

The face that kind of looks like LBJ ! ? ! ? :shock:

BB, development of water based life?
Now, that, is an assumption,,,, :wink:

For those that think Mars lost it's atmosphere due to a "solar wind", you should check out Venus's magnetic field.

Now [url=http://themis.asu.edu/mars-bin/mars_cgi_map.pl?TOP_LAT=90&LEFT_LON=226.0620016&CENT_LAT=35.98864486&CENT_LON=46.0620016&DISP_RES=2&DISP_DATASET=Visible&DISP_MAP_DATASET=3&DISP_MAP_PROJ=0&DISP_ZL=1&TNAIL_LINK=20050722a&PAN_SELECT_ZOOM=ZOOM&MAP_DATASET1.x=28&MAP_DATASET1.y=5]this[/url] is a map. One of my "tools".

[quote="Bad Buoys"]But what is this face doing in the rim of this crater?[/quote] What face? This one: :shock: ?

Cool image with great detail.
Gotta add it to my favorites as [url=http://antwrp.gsfc.nasa.gov/apod/ap010628.html][color=blue][u]Martian Terrain[/u][/color][/url] under "TOOLS"

But what is this face doing in the rim of this crater? Corporate advertising?
[url]http://ltpwww.gsfc.nasa.gov/tharsis/Mars_topography_from_MOLA/M_-20_-10_60_70.html[/url]

The aforementioned [url=http://antwrp.gsfc.nasa.gov/apod/ap050228.html][color=blue][u]2005 Ferbruary 28[/u][/color][/url] caption indicates past, huge oceans.

So if water based life ever developed on Mars; then wouldn't evidence of the last evolutions of any such life, no matter where it originated, expect to be found at the deepest points, in or around that last remaining water pools?

to Zigota, perhaps once you clicked it to zoom, you could then copy address from address bar and copy here? Like http://ltpwww.gsfc.nasa.gov/tharsis/Mars_topography_from_MOLA/M_40_50_50_60.html or something.

To Nedkelly's question about larger pools covered with dust:

Look at APOD Feb 28 2005 and see what you think.

http://antwrp.gsfc.nasa.gov/apod/ap050228.html

William Hartmann wrote an excellent book, [url=http://www.amazon.com/exec/obidos/tg/detail/-/0761126066/qid=1122192447/sr=8-1/ref=sr_8_xs_ap_i1_xgl14/104-8231865-6323164?v=glance&s=books&n=507846]The Traveler's Guide to Mars[/url], that goes over many theories on how Mars aquired and lost its water. This book was written prior to the Mars Exploration Rover mission, but its conclusions are still relevant. Hartmann and other planetary scientists deduced correctly from various satellite photos that Mars was once a water covered planet, and that water was responsible for many surface features, some more recent than you might expect.

A quick summary is that Mars, like the Earth aquired water either from volcanism, comets, or both. Mars lost its water due to the fact that its planetary magnetic field failed about a billion years after the planet formed. Unlike Earth which is protected from the solar wind by our planetary magnetic field, the solar wind was able to slowly strip away the atmosphere on Mars. As more of the atmosphere was stripped away, the atmospheric pressure dropped. This caused two things to occur: the greenhouse effect on Mars ceased to function causing the planet to cool down, and water either evaporated or sublimed into the atmophere where it was eventually stripped away. This is what has created the dead planet we see today.

The reason for the failure of the planetary magnetic field is uncertain, but it probably relates to the surface to volume ratio of Mars. Having a greater surface to volume ratio, Mars cooled down from its initially hot primordial matter. This eventually caused part or all of an iron core to solidify which stopped the magneto effect creating the planetary magnetic field. The reason this hasn't happened on Earth is that we have a balance between the lesser cooling due to the surface to volume ratio of our planet and the very small heat generation rate due to very small quanties of natural radioactive isotopes decaying thoughout the volume of our planet. In addition, the crust and the atmophere provide a very good layer of insulation.

Hope this helps. I hope you check out Hartmann's book if only for the beautiful pictures.

There is a large crater at about 70' in the upper center of this image ( http://antwrp.gsfc.nasa.gov/apod/ap010628.html ). I believe that is the crater in question. Click on that crater to zoom in. :wink:

To Zygote;
My question is, why should I go to [url=http://antwrp.gsfc.nasa.gov/apod/ap010628.html]Astronomy Picture of the Day 2001 June 28?[/url]

There is no relevant data to the icy crater there.

Now IF we had the Lat and long of the icy crater we could possibly find out more information about the area. But, alas, we don't.

Go to Astronomy Picture of the Day 2001 June 28 :wink:

The given data are as follows;
The crater is 35 km wide.
Located about 70 degrees north of equator.
Crater walls are about 300 m high.
The water ice is about 200 m thick.
The image is in color, resolution not too good, and the information we really need is sadly lacking for any more research concerning this region and location on Mars.
MOLA data would be nice to have, as would Lat. and Long. of the crater. THEMIS passes should indicate if any recent heat was there. So many questions, so little data.

Need more input,,, yet it remains a very intriguing picture.
Great comments about the potentials and possibilities of how this water may have come to the surface.

If this is an upwelling over a larger, buried pool, then the dark area at 11:00 might be a peak sticking up through, possibly a "martian island". The most significant dust accumulation seems to be to the left (North?) of this spot, possibly indicating something about wind patterns around this peak. I agree with nedkelly that the shadow suggests a pretty good dome to the overall ice structure. What a great photo.

My amateur two cents:

I would agree that upwelling is the source of the pool, and that the center of the circles is where it is coming from. The ice color shading and light angle suggest significant "doming"

And I would agree that the dust observations suggest this is recent. It also appears that there is some dust on the frost around 1:00 through 3:00 about half way down the crater wall.

Now my questions. Is there a big layer of dust over a larger pool? In the area from 7:00 through 9:00 at the base of the crater, there is a suggestion of more circles. Perhaps more ice circles covered with dust?

And another question on focus/resolution. The crater rim and ice circle details seem fairly "sharp". However, most of the right hand crater floor appears much "softer". Is this a picture artifact or further indication of dust covering ice?

Otherwise this is a great image - and has become my current screen wallpaper (as do many APOD images),

JF

I wondered about the dust issue as well. It seems like there are some patches of dust along the edges, and most significant in the upper left. It looks to me like the ice field has some pretty sharp edges (cliffs?) That would seem to argue against recent upwelling. Is it possible we are seeing a layer of frost covering the dust? Also, any idea what the dark circles are, such as the one near the edge at about 5 o'clock ?

As my first post here I would like to comment on the ice crater image of APOD July 20, 2005.

To get this clear of a view of water ice wouldn't it have had to form after any dust storm in that area? As there is no evidence of seepage I would have to advise that the formation was from an up welling. And, recently.

If memory serves me correctly, the last great dust storms were in 2000-2001 or back in 1970?

[quote="[url=http://asterisk.apod.com/viewtopic.php?t=609]Zygote from Mars[/url]"]:idea: I noticed in this image (Water Ice in a Martian Crater displayed on 2005 July 20) that there is a hole in the edge of the ice. Also, there appears to be rings radiating out from the hole suggesting that there is a heat source beneath the rim of the ice which melts it in varying degrees over time, creating these rings as the water refreezes. Was this crater created by a volcano or by meteor impact? Could this be a hot spring generated by minor volcanic activity? This might explain how some of the water on Mars reaches the surface. I would love to hear everyone's comments on this because I have yet to find any professional opinion on these anomalies. :roll:[/quote]

The H2O most likely is seepage of melting ground water, there is no evidence that water ever precipitated from clouds on Mars. Evidence of water/water erosion is found mostly in lower elevations, water/water erosion in the higher elevations all appears to start from hillsides meters below the surface. Impacts, volcanoes and an occasional heat wave are the causes of the subsurface water to melt.

U could check out the nasa website for that information...

Hi,

I was wondering what was the origin of the water on Mars and how (if at all) it was precipitated.