Isotopic evidence for the presence significant quantities of liquid water on Mars in the past comes from the observation of
A) an elevated ratio of deuterium to hydrogen
B) an elevated ratio of hydrogen to deuterium
C) a complete absence of hydrogen in the atmosphere
D) a complete absence of deuterium in the atmosphere

Question

Quizplus · Accepted Answer

The elevated ratio of deuterium to hydrogen is indicative of the presence of significant quantities of liquid water on Mars in the past, as the heavier deuterium is preferentially retained in water molecules compared to hydrogen. This isotopic signature is consistent with observed features on Mars such as valley networks and ancient lakebeds.

Isotopic Evidence for the Presence Significant Quantities of Liquid Water