Ceres and some of the moons of Jupiter are covered in a thick layer of water ice
- below which there may be a deep layer of liquid water.
The images below show Mars as it is today. When Earth was at the same orbital position
(and the same diameter) as Mars, some 330 million years ago during the Carboniferous
Period, complex life existed. Fossils of tetrapods have been found within a narrow
band which encircled the Earth and this band will have had the magnetic equatorial
line at its centre.
So Earth, with its vast accumulation of water, would have looked very different to
Mars. It will have been a ‘snow-ball’ save for a narrow equatorial belt .
I have created an artist’s impression below of how the Earth may have looked at the
time. Here I have superimposed the ice sheets over the Mars image.
The maximum temperatures on Mars, around the equatorial region, vary from 25 degrees
C in the summer to much cooler temperatures in the winter time, so the equatorial
band depicted on the Pangaean Earth will have increased and decreased its width,
seasonally. Much of the plant life establishing itself over wider areas in the summer
time will have been covered and compacted by ice in the winter time.
Water Formation by Methanogens
The following reaction describes how methane and water are produced from hydrogen
and carbon dioxide by methanogens during their metabolism.