Oceans of the Solar System - Ocean Worlds: The Story of Seas on Earth and Other Planets - page 217

invoked a thick atmosphere, charged with heat-trapping gases such
as water vapour.
Arrhenius, among his other accomplishments (he won a Nobel
Prize in 1903 for his early work on the nature of electrolytes in solu-
tion 123 ), was a pioneer in the study of greenhouse gases, being the first
to propose that past changes in the Earth's carbon dioxide concentra-
tions had caused the Ice Ages. He examined the available evidence for
a thick, heat-retentive atmosphere on Mars by considering the most
painstaking spectroscopic measurements of Mars then made to try to
detect water vapour. From Earth this was difficult to measure, then as
now, because of the obscuring effect of water vapour in the Earth's
own atmosphere (see Chapter 1). Nevertheless, to Arrhenius the data
were clear. The Martian atmosphere was thin, with very little water
vapour—and so the planet was essentially deep-frozen, with little
chance of any but the simplest and sparsest life forms. Arrhenius did
not dispute that huge natural valleys might exist, but ascribed them to
tectonic activity and not to an alien civilization. He also thought that
at the base of these natural canyons, and in low-lying areas, there
might be a little liquid water—especially if it was a sufficiently con-
centrated brine, charged with dissolved salts, to resist freezing. Regard-
ing Lowell's vision—of cities 50 times bigger than London, and of a
planet made red by autumnal leaf change, as in New England during
the fall—he was politely scathing. The trouble with explanations like
those, he said, is that they explain everything, and therefore they
explain nothing. 124
Arrhenius had more trouble with Venus. This planet is the bright-
est object in the night sky after the Moon. It had been known from
ancient times: a seventh century bc Neo-Assyrian cuneiform text
from the British Museum records astronomical observations of
Venus, the 'bright queen', from 1,000 years earlier. At 95 per cent the
diameter of Earth, and a little over 80 per cent of its mass, it is Venus