ASTROBIOLOGY Volume 2, Number 1, 2002 © Mary Ann Liebert, Inc. Hypothesis Paper Biogenesis and Early Life on Earth and Europa: Favored by an Alkaline Ocean? STEPHAN KEMPE 1 and JOZEF KAZMIERCZAK 2 ABSTRACT Recent discoveries about Europa—the probable existence of a sizeable ocean below its ice crust; the detection of hydrated sodium carbonates, among other salts; and the calculation of a net loss of sodium from the subsurface—suggest the existence of an alkaline ocean. Alka- line oceans (nicknamed “soda oceans” in analogy to terrestrial soda lakes) have been hy- pothesized also for early Earth and Mars on the basis of mass balance considerations involving total amounts of acids available for weathering and the composition of the early crust. Such an environment could be favorable to biogenesis since it may have provided for very low Ca 21 concentrations mandatory for the biochemical function of proteins. A rapid loss of CO 2 from Europa’s atmosphere may have led to freezing oceans. Alkaline brine bubbles embed- ded in ice in freezing and impact-thawing oceans could have provided a suitable environ- ment for protocell formation and the large number of trials needed for biogenesis. Under- standing these processes could be central to assessing the probability of life on Europa. Key Words: Biogenesis—Ocean chemistry—Soda ocean—Alkalinity—Europa—Lake Van. Astro- biology 2, 123–130. 123 INTRODUCTION B IOGENESIS is one of the most puzzling scien- tific problems. Given life’s biochemical com- plexity, it is a wonder it ever arose. Even if Panspermia (Hoyle and Wickramasinghe, 1997) is accepted as a way to propagate life, it does not solve the fundamental problem of biogenesis but shifts it from the Solar System to other places in the galaxy. Searching for life or its biogeochemi- cal signatures on Europa (e.g., Phillips and Chyba, 2001) challenges our understanding of biogenesis in general and may lead to an im- proved understanding of biogenesis on Earth. Re- cent discoveries about Europa suggest that evi- dence of events that occurred in the early phases of the Moon’s history may still exist. Europa most probably hides a sizeable ocean below its ice crust (e.g., Anderson et al., 1998; Greeley et al., 1998; Pappalardo et al., 1999; Kargel et al., 2000); hy- drated sodium carbonates, among other salts, have been detected on Europa (McCord et al., 1998, 1999); and it has been calculated that a net loss of sodium occurs from Europa’s surface (Johnson, 2000). These discoveries, which suggest the existence of a hypocryotic, alkaline ocean, could be central to assessing the probability of life on Europa. Furthermore they are consistent with 1 Institute of Applied Geosciences, University of Technology Darmstadt, Darmstadt, Germany. 2 Polish Academy of Science, Institute of Paleobiology, Warszawa, Poland.