Rosetta Space Probe And Philae Module, 67P/Churyumov–Gerasimenko Comet, European Space Agency

Upon landing on the comet, Philae will also test some hypotheses as to why essential amino acids are almost all "left-handed", which refers to how the atoms arrange in orientation in relation to the carbon core of the molecule. Most asymmetrical molecules are oriented in approximately equal numbers of left- and right-handed configurations (chirality), and the primarily left-handed structure of essential amino acids used by living organisms is an anomaly. One hypothesis that will be tested was proposed in 1983 by William A. Bonner and Edward Rubenstein, Stanford University professors emeritus of chemistry and medicine respectively. They conjectured that when spiralling radiation is generated from a supernova, the circular polarization of that radiation could then destroy one type of "handed" molecules. The supernova could wipe out one type of molecules while also flinging the other surviving molecules into space, where they could eventually end up on a planet.
Reaction control system problems
In 2006, Rosetta suffered a leak in its reaction control system (RCS). The system, which consists of 24 bipropellant 10-newton thrusters, is responsible for fine tuning the trajectory of Rosetta throughout its journey. The RCS will operate at a lower pressure than designed due to the leak. This may cause the propellants to mix incompletely and so burn 'dirtier' and less efficiently, though ESA engineers are confident that they have sufficient fuel reserves to allow successful completion of the mission.