英语听力：探索发现 科学新发现：我们的大气层-26（在线收听）

 bubbles in the atmosphere.On other planets with denser atmospheres,larger, more complex creatures can take to skies.The thick air could support them alofty,allowing bulky reptiles to fly and glide.This creature probably couldn't be able to fly very low on our planet.But even on a planet like Titan for instance,it has a surface gravity only about 50%of earth but atmosphere density at the ground level about 1.5times,even a man with wings straped on his arms could fly in atmosphere like this.So we could have creatures like this.Hegon bases his ideas on known planets and evolutionary history of earth.But it's all pure speculation untill we find life in alien atmopheres. I could be pretty thrilled,just find microbes and rocks on Mar's for instance.They don't have what kind of shapes and meat to get my blood up.I would be pretty happy to just know that life has happened twice. At present,we are alone,life may have happened just this once.And if it did,it's only because of our unique planet atmosphere.As we have soared for miles above the ground, we have journey through the ocean of air.The air would shields us,supports us and sustains us with every breath.