THE ORIGIN OF LIFE ON EARTH
No o ne has yet figured out exactly how Earth passed from a state of having all the chemical building blocks necessary for life to a state where life actually existed. But the change, while enormously important, may not have been all that much of a leap.
Oldest rocks in the world are about 3.9 billion years old, and ones showing fossil traces of life are barely younger. This suggests (rather unlikely), or it
arose even earlier. In any case, the date is it important bevause at that time .the Solar System was still a pretty hostile place. Large, devastating, impacts by asteroids and comets were frequent, and Earth's surface looked more like the Moon's southern highlands than like any landscape on Earth today.
From what we know about today's Earth, life is outstandingly tenacious, adaptable, and resourceful. Given this tenacity, it is possible that life actually started on Earth several times, but was wiped out by impacts on each attempt but the last.
What does this say for the chances of finding life else-fey where, either in the Solar System or outside it? Actually, the chances look fairly good. Astrophysics shows that chemistry . is chemistry the universe over, so nature ought to be able to duplicate in another place the pathway that led to life on Earth. But whether life can persist elsewhere, and for how long, we can only guess..