Mars Rovers' Images

"George Dishman" skrev i en meddelelse
...

snip

Terrestrial tektites get their shapes from aerodynamic
effects, no? Less Martian air, more spherical shape, yes?

Less air and drag means the material might be near to
weightless in flight. There has been some talk about
single small marks on each spherule. Might these be
due to the formation of a trapped bubble as dissolved
gas is released during cooling?

If the spheres has solidified a spheric shape, it could still be somewhat
soft at landing and produce the more subtle imprint that that indeed gives
an impression of a common biological a-spheric abnormality (.. now where was
the picture...). The later sedimentary history of the spheres may well give
surficial fractures.

Carsten

The reduced bouyancy
might make it less able to breach the surface which
would also be the first to cool.

George

Ian Goddard
I'm beginning to form a personal opinion that a lot of observations may
conform to a large impact of an ice-meteor, but I have no experience that
applies to the early stage of such an event, but may expect such an
incidence to account for volcaniclastic structuring of the solid outcrop at
the Opportunity-site. I have expressed surprise that Mars was not 'dustier'
(fine-grained material is expected as the endproduct of prolonged windy
abrasion, imho) and has suspected a mainpart of the spheres to be the 'sink'
for such products. My overall idea is, that energy-release, ice and dust
should contain the constituents in a scenario that evolves large amounts of
spheres in a free fall process. I'm not the best to account for the details
though. I'm not a Mars or planetary specialist.

Carsten

"Ian Goddard" skrev i en meddelelse
...
"Paul Henney" wrote:

Ian,

I had similar thoughts.

However the size and shape distribution is unusual..all the tektites in
my
collection have very variable shapes. I would have expected to see some
more
irregular shapes from melt droplets.


Right, these Martian spheres are remarkably similar in size and shape.
However, dissimilarities between Mars and Earth (not to mention
between different impact events) might account for the differences you
observe. Consider that the paper I cited by R.D. Lorenz

http://www.lpi.usra.edu/meetings/5thMars99/pdf/6039.pdf

notes dissimilarities between microtektite formation on Mars versus on
Earth. For example, on Mars, impacts energetic enough to produce only
2.5-km-diameter craters may produce microtektite while 10 km craters
are necessary on Earth. With more impacts producing microtektites,
Lorenz predicts that microtektites "should therefore be widespread on
Mars." He also observes that: "for Mars, with lower escape velocity
and further from the sun, such velocities are lower than for Earth,
and so spherules are larger." Spherule size is also "limited by
surface tension's ability to overcome aerodynamic stress," and thus
Mars' thinner atmosphere should also affect spherule formation
differentially. These factors suggest that spherules on Mars may be
both more abundant and structurally different than spherules on Earth.




On the "berries" that have been sliced open there dosen't seem to be any
zoning or indeed any kind of structure..the structure is really
isotropic.

Correct. In these images from Opportunity we first see some
"blueberries" embedded in rock. Subsequent images show the same
rock after being subject to Opportunity's Rock Abrasion Tool that
reveals a cross-sectional view of the interior of the sphe

http://marsrovers.jpl.nasa.gov/galle...nity_m034.html


Ian Goddard's Journal: http://iangoddard.net/journal.htm

"When we have lived any time, and have been accustomed to
the uniformity of nature, we acquire a general habit, by
which we always transfer the known to the unknown, and
conceive the latter to resemble the former." David Hume

"Carsten Troelsgaard" wrote in message
k...
Ian Goddard
I'm beginning to form a personal opinion that a lot of observations may
conform to a large impact of an ice-meteor, but I have no experience that
applies to the early stage of such an event, but may expect such an
incidence to account for volcaniclastic structuring of the solid outcrop
at
the Opportunity-site. I have expressed surprise that Mars was not
'dustier'
(fine-grained material is expected as the endproduct of prolonged windy
abrasion, imho) and has suspected a mainpart of the spheres to be the
'sink'
for such products. My overall idea is, that energy-release, ice and dust
should contain the constituents in a scenario that evolves large amounts
of
spheres in a free fall process. I'm not the best to account for the
details
though. I'm not a Mars or planetary specialist.

Carsten

Mars is very dusty. The fact that it doesn't appear to be too dusty at the
two rover landing sites is not a mistake. These two sites were selected in
part because they weren't very dusty. Both areas, especially at Gustev,
have high incidents of dust devils, which tend to sweep a lot of the dust
from the surface.