The picture of the pasta feature in rock on Mars alone is a strong case for
prior organic structure.
It is symmetric and it is a real stretch to think that it was or is
inorganic and formed like that.
It would be the craziest crystalization process ever witnessed by inorganic
material ever if it is.
There is no known analog on earth of such crystalization. Magma that
somehow was squirted into
that shape is really hard to believe. In the low gravity environment, it
would be impossible to get symmetry
like that.

The other argument for an organic beginning is far more real. The problem
is, there is only one so far. If it is
a fossil, there should be more