Pennsylvania State University
Department of Geosciences
437 Deike Building
Alfred P. Sloan Scholar
Bunton Waller Scholar
email: rmr5265 att psu.edu
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- Extrasolar planet habitability
The habitable zone (HZ) is defined as the region around the star where water can be sustained as a liquid on a planetary surface (Kasting et al., 1993). The conservative boundaries of the HZ are defined by the moist greenhouse limit at the inner edge and the maximum greenhouse limit on the outer edge (ibid). I have developed an improved 1-D radiative-convective climate model and, together with Ravi Kopparapu, have recalculated the HZ boundaries for F-M main sequence stars (Kopparapu and Ramirez et al., 2013). For our solar system, the HZ boundaries are at 0.99 – 1.67 AU, compared to the 0.95 – 1.67 AU obtained by Kasting et al. (1993). In Kasting et al. (2013), we argue that the traditional habitable zone edges, originally defined by Kasting et al. (1993), are what observers should be using in locating habitable exoplanets. We continue to refine the habitable zone as new scientific developments unravel.
(Click above image for full resolution version)
- Early Mars atmospheric evolution
The presence of valley networks on the surface of Mars strongly suggests that the Red Planet was warm enough to exhibit liquid water on its surface at or before 3.8 billion years ago (i.e. Craddock and Howard, 2002). However, climate models have had difficulty producing a feasible greenhouse climate scenario which would have kept early Mars warm with the fainter young Sun. We propose that a CO2-H2 greenhouse could have done the trick (Ramirez et al., 2013a). I am also interested in demonstrating that leading cold Mars hypotheses (i.e. Segura et al., 2008) cannot explain the observed surface geomorphology.
- Earth studies
The value in studying Earth to learn more about other planets cannot be overstated. In Kopparapu and Ramirez et al. (2013), we calculate the inner edge to be precariously close to Earth’s orbit (0.99 AU). However, we had assumed fully-saturated atmospheres, which overestimates water vapor absorption for Earth. In our most recent work (Ramirez et al., 2013b, in review), we utilize a more realistic relative humidity distribution to address whether or not Earth is truly susceptible to either a moist or runaway greenhouse.