Astronomers say they now know, what many of us have long suspected, and it is that our planet's water did not come from the comets.
Results from the Rosetta probe suggest the old theory doesn't hold water. Or if it does, it's the wrong kind of water.
Some scientific diehards are now suggesting that maybe the water is "deep inside" the comets or that it arrived here on "wet asteroids". This modification of the comet-earth-water-theory is definite proof of the drowning-man-will-grasp-at-a-straw-theory.
One answer to the riddle is the theory that the water burst forth from deep inside the Earth. And there is actual evidence for this theory.
Scientists at Vienna University suggested earlier this year in the science magazine Nature that there could as much water deep below the Earth's surface as on the surface.
Their calculations are based upon the fact that diamonds from great depths brought to the surface by volcanic activity in South America were found to contain water.
However there are some who believe they have known the truth about the source of the water all along.
They say that the whole of our blue planet was originally covered with water. That there was water above the Earth and water on the Earth and in between the two lots of water was a layer of atmosphere.
This idea is not far fetched when one looks for example at the rings around other planets.
The author of the account of Creation in the book of Genesis speaks of:
of our blue Earth
of a layer of water
in the sky
and of water below
between the waters
like an ancient atmosphere
under the expanse
to one place
let dry ground appear
the gathered waters