The reason that the planet Mars appears red in color is due to the massive presence of the element iron. Mars has so much of iron on its surface that the barren rocks on the surface tend to rust with exposure to the oxygen over a huge period of time.
Although Earth also has rich deposits of iron in the crust, some process is not letting the planet to appear as red as Mars. Earlier theories claimed that the process that by which iron is removed from magma/rocks involved volcanoes. Scientists have long believed that magnetite was the mineral that ingests iron from the molten magma deep beneath the surface of the Earth.
However, now, a new study conducted by a research team at the Rice University in Texas claims that garnet is the original component that eats away the iron.
“The accepted wisdom is that magnetite pulls iron from the [magma] melt before the melt rises and gets erupted out at continental [volcano] arcs,” said Prof. Ming Tang, the lead author of the study. “Iron depletion is most pronounced at continental arcs, where the crust is thick and much less so in island arcs, where the crust is thin.”
According to Prof. Tang, if magnetite would have been responsible for the loss of iron then it would have been available in abundance in the places where the crust is thicker. But, interestingly, the magnetite level does not seem to correspond to the thickness of the crust. He added that the abundance of garnet does correspond aptly to the crust’s thickness. The research team found garnet to be in abundance below the continental arcs and iron to be relatively less in that area.
“This is born out in the global record, but the evidence is something that wouldn’t be obvious from looking at just one or two cases,” Tang said.
The research study has been published in the Science Advances journal.