How many are there in a book? http://freeones.in.net/ freeones.com This accumulation of heavier isotopes, or isotopic enrichment, is prominent when looking at the levels of hydrogen in the Martian atmosphere. Curiosity found much more deuterium, a heavier isotope of hydrogen, than what you would see on Earth. "The ratio is about five times higher," said Chris Webster, the lead investigator behind the Tunable Laser Spectrometer, one of SAM's instruments.