Scientists have found living organisms trapped in crystals(晶体) that could be 50,000 years old.
The organisms were found in a hot, but beautiful cave system in Naica, Mexico. These ancient life forms can be seen only with a microscope. Penelope Boston, who leads the Astrobiology Institute at NASA, the space agency of the United States, says the ancient microbes(微生物) were able to live by eating minerals such as iron.
She spoke about the discovery recently at a meeting of the American Association for the Advancement of Science. If the findings are confirmed, they will show how microbes can survive in extreme conditions. Forty different kinds of microbes and some viruses were found in the underground area. The genetic structures of these organisms are 10 percent different from those of their nearest relatives.
The caves in Naica are 800 kilometers deep. They were once used for mining lead. Before the miners began working in the caves, the area was separated from the surface and the outside world. Some of the caves are as big as the large religious centers built during Europe's Middle Ages. There are crystals covering the walls. The caves are so hot that scientists must wear special clothing to keep cool. The clothing keeps the crystals safe from human germs（病菌）or other damage. Boston said the researchers could only work for about 20 minutes at a time before they had to go to a room that was 38 degrees Celsius to cool down.
NASA officials would not let Boston share her findings with scientific experts before last week's announcement. So scientists could not say much about the findings. But Norine Noonan, a biologist with the University of South Florida, said she believed them. "Why are we surprised?" Noonan asked. "As a biologist, I would say life on Earth is extremely tough and extremely colorful."
Boston is also studying microbes commonly found inside caves in other countries, such as Ukraine and the United States. These microbes appear to be impossible to kill. Boston said they show how difficult life on Earth can be.
