After its primary accretion had mostly finished, the proto-Earth underwent a catastrophic collision with a stray planetary embryo variably estimated to be at least equivalent to Mars’ mass (Theia). This event effectively reset Earth’s radiometric chronometers such as Pb-isotopes, and gave rise to the Moon. Since then, the Earth-Moon system has been subjected to collisions with smaller solar...
‘How did life choose its handedness?’ Just like our hands mirror each other, but cannot be superimposed on each other, amino acids and sugars exist in left- and right-handed forms. Even if there appears to be no biochemical reason to favor one enantiomer over the other, life on Earth uses almost exclusively left-handed amino acids and right-handed sugars. This is called biological...
