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Posted by: slinted Apr 30 2004, 08:15 AM

http://www.lyle.org/~markoff/collections/1P136264401EFF1500P2434L247M1.JPG
http://www.lyle.org/~markoff/collections/oppsol93pancam_enhanced.jpg

Posted by: cassioli Apr 30 2004, 09:31 AM

Guys... there are so many craters of so many different sizes that I wonder HOW could rovers have survived till now without being hit by a metorite!!! They are TOO MUCH, if you consider strong Martian winds... probably new ones are created every month (week? day?...).

Luca

Posted by: djellison Apr 30 2004, 09:46 AM

Every century - perhaps even less frequently.

The winds may be fast on mars - but the atmosphere is so very thing it has little force.

Most of the little dimples around here will probably be secondary craters from larger impacts anyway.

Doug

Posted by: SickNick Apr 30 2004, 09:53 AM

Cassioli,

Your argument actually works the other way.

SINCE the rovers have not been hit by meteorites

THEN the many craters must have accumulated over a huge time

AND erosion rates on Mars are VERY slow...

Posted by: Sunspot Apr 30 2004, 10:50 AM

These 2 NavCam shots are pretty spectacular, look like the rover may have driven towards the north rim.

http://qt.exploratorium.edu/mars/opportunity/navcam/2004-04-29/1N136441478EFF1800P1829R0M1.JPG
http://qt.exploratorium.edu/mars/opportunity/navcam/2004-04-29/1N136441478EFF1800P1829L0M1.JPG

There appears to be a bit of bedrock exposed on the rim that opportunity might be able to reach without doing into the crater itself.

Posted by: cassioli Apr 30 2004, 12:18 PM

Is it possible to make a comparison between Earth and Mars wind?
I mean: a 200 Km/h wind on Earth would easily take me away... How fast should a Martian wind blow to take me away?

Maybe we (you...) should express in better measure units: I suppose you can use pressure units, or others: "On Earth, a 100 Km/h wind would push a 1 m^2 area with 1 Newton force", or "would put a 1 Kg object a 1 g acceleration", or similar...

Luca

Posted by: Baltic Apr 30 2004, 12:42 PM

I don't think so. Seems to me Oppy is at the west rim looking to the southeast. There seems to be the heatshield in view.

Tom

Posted by: cassioli Apr 30 2004, 12:49 PM

I found an interesting page about wind:

http://www.jxj.com/magsandj/rew/2003_03/wind_turbines.html

It says the wind kinetic energy is:
E=0.5 * r * A * u^3

r = air density
A = section area
u = velocity

As Mars atmosphere has 1/1000 of Earth's atmosphere density (I think: 1/1000 pressure = 1/1000 density?!?), I think this means that Martian wind has 1/1000 of equivalent Earth wind power. Is it right? If it was true, this would mean that a 180 Km/h Martian wind would be equivalent to 0.18 Km/h Earth wind! I think there is something wrong, can you help?

Luca

Posted by: djellison Apr 30 2004, 12:57 PM

Typical earth density = 1000 mbars

Typical Mars Density = 6 - 12 mbars - typically 8

Thus, approx 0.8% the density - or 8 1/1000ths

Doug

Posted by: cassioli Apr 30 2004, 01:13 PM

... 10 is easier!
So, Mars wind has 1/100 of the power of Earth wind?
So, a 200 Km/h Mars wind has the effect of a 2 Km/h Earth wind?

Luca

Posted by: GJG Apr 30 2004, 04:47 PM

Luca, don't think that will work -- velocity term is cubed -- can't play with both terms in a linear manner. At the same velocity, the energy is 1/100 but at high velocity even mars' wind could get rough.

Greg