(ËvÉr bÉl) adj. 1. of or consisting of words: verbal ability. 2. spoken rather than written; oral: verbal communication. 3. concerned with words only, rather than with the ideas, facts, or realities expressed: a purely verbal distinction. 4. corresponding word for word; verbatim: a verbal translation.
Because their hypothesis requires that Earth arose from water-containing materials already present in the inner solar system, it's called the wet-accretion hypothesis. Most of Earth's water has an indigenous origin, says Drake.
Follow the water. Scientists can track the origin of Earth's water by looking at the ratio of two isotopes of hydrogen, or versions of hydrogen with a different number of neutrons, that occur in nature.