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Home , Gliese 581

EXOPLANETS, AND HABITABILITY

Eduardo Janot Pacheco, Luander Bernardes

Institute of Astronomy, Geophysics and Atmospheric Sciences, Department of Astronomy, University of São Paulo, BRAZIL

and Claudia Lage

Institute of Biophysics Carlos Chagas Filho, Rio de Janeiro Federal University, BRAZIL

FSLife Gainesville, April 3-6 1 PURPOSE OF THE WORK:

ESTIMATE OF  Average Surface

 CO2 Partial Atmospheric Pressure pCO2 as a free parameter,  For in the Habitable Zone (HZ) For hypothetical moons of gaseous giants known to be in the HZ

 EXOPLANETS + TERRESTRIAL

 FSLife Gainesville, April 3-6 2 GREENHOUSE EFFECT

(data base: J. Schneider’s http://exoplanet.eu/) INPUT: The Extrasolar Encyclopedia  Williams (1997) atmospheric model for the (geodynamic conditions, Si-Ca cycle, ...)

Exomoons of gaseous giants in the HZ with an atmosphere, dynamic stability, geodynamic activity...

  RESULTS:

1) more precise determination of HZ

2) New concept: the EXTREMOPHILIC ZONE: FSLife Gainesville, April 3-6 3 EZ

Energy Budget Equation of the atmospheric model:

where

L(t) is the stellar , d the orbit size, A the atmospheric albedo, which is a fonction of the surface albedo as surface temperature Ts , stellar azimutal µ angle , CO2 partial pressure p and F the IR flux leaving the planet.

FSLife Gainesville, April 3-6 4 Basic Equations for the exomoons model:

1) Stable orbital radii (Domingos et al., 2006):

for prograde orbits and

for retrograde orbits. RH is the exoplanet Hill radius.

FSLife Gainesville, April 3-6 5 Basic Equations for the exomoons model (cont.):

Maximum exomoon (Murray & Dermott, 2000; Barnes et al. 2009):

Where f, Qp and k2p are parameters adjusted empirically, T is the time scale for the moon orbital decay and a, M and R are the orbital semi-major axis, and radius of the planet and moon.

FSLife Gainesville, April 3-6 6 EXTREMOPHILES: under extreme conditions

FSLife Gainesville, April 3-6 7 Radiococcus radiodurans: endures 10,000 times the radiation dose lethal for humans

FSLife Gainesville, April 3-6 8 Experiment on

+ Solar UV + = 100µm

Carbon tape

= Microastronauts?

Lima et al. 2010; Lima et al. Concordia 2011 micrometeoriteFSLife Gainesville, April 3-6 9  

 THE EXTREMOPHILIC ZONE (EZ), A NEW CONCEPT : “EZ IS THE TEMPERATURE REGION AROUND A WHERE (TERRESTRIAL) EXTREMOPHILES COULD LIVE ”

EZs are obviously more extended than HZs.

FSLife Gainesville, April 3-6 10 SOME RESULTS a) for rocky supposed to be in the HZ

< b) for hypothetical moons around gaseous giants in the HZ

FSLife Gainesville, April 3-6 11 Results for the

Look out!

Earth will be outside < both the HZ and EZ in 1.7 G years from now for any reasonable CO2 partial pressure. will then be inside the EZ.

FSLife Gainesville, April 3-6 12 Habitability in the Solar System HZ: 273K

FSLife Gainesville, April 3-6 13 13 Habitability in the Solar System (cont.)

FSLife Gainesville, April 3-6 14 14 Habitability in the Solar System (cont.)

FSLife Gainesville, April 3-6 15 15 Results for the Solar System

Look out!

Earth will be outside < both the HZ and EZ in 1.7 G years from now for any reasonable CO2 partial pressure. Mars will then be inside the EZ.

FSLife Gainesville, April 3-6 16 Analysis of habitability for the Gl 581 System Mayor et al. 2008: “GL 581c is in the HZ” (GL 581d is a super-Earth with 6 M ) Earth

FSLife Gainesville, April 3-6 17 17 Analysis of habitability for the Gl 581 System (cont.) GL581d can hardly be in the HZ

FSLife Gainesville, April 3-6 18 18 Analysis of habitability for the Gl 581 System (cont) GL 581 b is in the EZ

FSLife Gainesville, April 3-6 19 19 Habitability in the of (M3V)

Super-Earth planet “d” (6 MEarth) stays in HZ and EZ from 2.2 G years on. But, it is outside the HZ for any< reasonable CO2 partial pressure. Nevertheless, the planet is in the EZ even for small CO2 pressures as e.g. on Earth (3x10-4 bars).

FSLife Gainesville, April 3-6 20 Analysis of habitability for the HD 37124 System G4V star

FSLife Gainesville, April 3-6 21 21 Analysis of habitability for the HD 37124 System (cont.)

FSLife Gainesville, April 3-6 22 22 Analysis of habitability for the HD 37124 System (cont.)

FSLife Gainesville, April 3-6 23 23 Analysis of habitability for the HD 37124 System (cont.)

FSLife Gainesville, April 3-6 24 24 Habitability in the planetary system of HD 37124 (G4V)

Planet “c” enters HZ after 6 G years but very high CO2 partial pressures are needed for it. <

It is always in the EZ for any CO2 pressure.

Exomoons with masses capable to maintain plate tectonics and an atmosphere are able to exist orbiting HD37124 c. FSLife Gainesville, April 3-6 25 HZ

EZ

Habitable and ExtremophilicFSLife Gainesville, zones April for 3-6 some 26planetary systems CONCLUSIONS

Using a model of an Earth-like atmosphere and a model for the orbital stability of exomoons, we show that terrestrial organisms can survive on the surface of planets and moons of extrasolar systems < in a region larger than the “classical” HZ.

 Definition of “Extremophilic Zone” (EZ) Next step: to use detailed atmospheric models with other free parameters to investigate the possible survival of extremophiles in these environments. THANK YOU!

FSLife Gainesville, April 3-6 28