About the double nature of the comet as recently discovered. It is anybody’s guess what the surface will reveal.
In spite of the uncertainties inherent in the present calculation, it is possible to interpret the surprisingly large outflow of water observed from the Comet 67P/C-G (Churyumov-Gerasimenko) on June 6, 2014, when the comet was between Jupiter and Mars, as being indicative of biology. Although microorganisms in comets are likely to be in a frozen dormant state at aphelion, a sporadic resumption of metabolism will occur near perihelion if subsurface melting can take place. Metabolism builds up subsurface gas pressures of thousands of atmospheres, which is enough to cause cracks in the surface crust releasing gas and dust. Such melting could occur due to increased solar radiation or, on occasion when impacts of smaller bodies transfer kinetic energy that can be converted to heat. Comet Hale-Bopp showed sporadic activity when it was outside the orbit of Jupiter. We can argue that this activity in Comet Hale-Bopp, as well as the new evidence from Comet Churyumov-Gerasimenko, point to the resumption of bacterial activity (8).
As we await the descent of the Philae lander onto Comet Churyumov-Gerasimenko with bated breath, there would inevitably be many surprises in store. The recent discovery that the comet has a “double” structure and is probably a contact binary may be the first of many to come. It is to be hoped that more indirect evidence of biology will be forthcoming as the ROSETTA mission draws to a conclusion this year.