What metric acts as the unique chemical fingerprint for comparing water from different solar system reservoirs?

Answer

The ratio of deuterium to normal hydrogen (D/H)

The comparison of deuterium (D), the heavier isotope of hydrogen, to normal hydrogen (H) provides a preserved chemical signature that helps scientists trace the origins of water.

What metric acts as the unique chemical fingerprint for comparing water from different solar system reservoirs?
OriginEarththeorywatercomet