小题1:About 16million years.
小题2:A distant dark twin of the Sun, called Nemesis.
小题3:10 percent of the Earth’s inhabitants wiped out.
小题4:Asteroids crashing into the earth.
小题1:About 16million years.
小题2:A distant dark twin of the Sun, called Nemesis.
小题3:10 percent of the Earth’s inhabitants wiped out.
小题4:Asteroids crashing into the earth.