A new study suggests Earth could have lost up to 60 percent of its atmosphere in the collision of space objects that created the moon. Most scientists believe this event happened about 4 billion years ago when Earth was still developing. They think a massive object, possibly the size of the planet Mars, hit the Earth, sending vaporized particles into space. Gravity is believed to have brought these particles together to form the moon. The study presents evidence that this collision might have caused Earth to lose between 10 to 60 percent of the atmosphere it had. A report on the study appeared in the publication Astrophysical Journal Letters.