Meridiani....where is the ejecta?

Meridiani has a very strange feature.
There are craters and no ejecta.

Is the ejecta all covered by some recent event? If so, why is the
surface surrounding the craters not lumpy?


Are the craters not impact events but sinkholes? The bottom of Eagle
crater had horizontal sedimentary rock the was cracked parallel to the
layering. This would make sense if the ground had sunk.

Opportunity is aproaching endurance crater which is pretty large, but
the surface looks smooth all the way to the drop off.

Mike Herron wrote in message ...
Meridiani has a very strange feature.
There are craters and no ejecta.

Is the ejecta all covered by some recent event? If so, why is the
surface surrounding the craters not lumpy?

Are the craters not impact events but sinkholes? The bottom of Eagle
crater had horizontal sedimentary rock the was cracked parallel to the
layering. This would make sense if the ground had sunk.

Opportunity is aproaching endurance crater which is pretty large, but
the surface looks smooth all the way to the drop off.

Craters age and change. Over time they lose their
ejecta blankets and slump. This is true even on the
Moon where impacts of various sizes (ranging upwards
from near continuous bombardment by micrometeoroids)
disturb the surface. On Mars there is also the wind,
wind-borne dust, and, potentially for older craters,
water. In fact, the lack of an ejecta blanket is not
at all an unusual feature for craters on Mars, it
merely indicates it is an old crater that has lost
its ejecta blanket due to weathering. More so, a
sink hole that would be so nearly circular and
otherwise mimic the appearance of a crater so closely
would be tremendously unusual.

In article ,
says...
Mike Herron wrote in message ...
Meridiani has a very strange feature.
There are craters and no ejecta.

Is the ejecta all covered by some recent event? If so, why is the
surface surrounding the craters not lumpy?

Are the craters not impact events but sinkholes? The bottom of Eagle
crater had horizontal sedimentary rock the was cracked parallel to the
layering. This would make sense if the ground had sunk.

Opportunity is aproaching endurance crater which is pretty large, but
the surface looks smooth all the way to the drop off.

Craters age and change. Over time they lose their
ejecta blankets and slump. This is true even on the
Moon where impacts of various sizes (ranging upwards
from near continuous bombardment by micrometeoroids)
disturb the surface. On Mars there is also the wind,
wind-borne dust, and, potentially for older craters,
water. In fact, the lack of an ejecta blanket is not
at all an unusual feature for craters on Mars, it
merely indicates it is an old crater that has lost
its ejecta blanket due to weathering. More so, a
sink hole that would be so nearly circular and
otherwise mimic the appearance of a crater so closely
would be tremendously unusual.

Agreed - except for the comment in re sinkholes. I am convinced that
many of the features on the plains are, indeed, sinkholes. The troughs
and crater chains that appear as extensions of the troughs are almost
definitely sinkhole-type formations, IMHO.

However, it's pretty certain that Endurance is an impact crater. Eagle
is *probably* an impact crater, and Fram is definitely an impact crater.
I'd say Fram is the most obvious, and possibly freshest, impact crater
they've seen -- it does have very obvious and well-developed ejecta.

Doug