Mars is no stranger to life. Seven U. S. spacecraft have successfully landed there, and all of them took microbes to the planet’s surface(though the bugs probably did not survive for long). Yet the world’s space agencies continue to maintain strict spacecraft sterilization (消毒) procedures in the hope of minimizing the spread of Earth life beyond our planet. For decades this idea — known as planetary protection—is widespread. Now, some scientists say, these procedures are preventing the search for life beyond Earth by raising costs and preventing innovative missions-without meaningful benefits.
Of all missions to Mars to date, only the Vikings, the first trip to the Red Planet, were intended to test for life. Spacecraft that went later did not have that ability. But a future mission will, and the protectionist thinking goes, a spacecraft might not be able to distinguish between a life form native to Mars and one with origins on Earth. In July 2013 astrobiologists Dirk Schulze-Makuch and Alberto Fairen argued against this in Nature Geoscience.
“If Earth life can thrive on Mars, they almost certainly already do,” the authors write. “If they cannot, the transfer of Earth life to Mars should be of no concern, as it would simply not survive.”
With clear evidence of a water y history and some signs of water present, Mars could be where we find life in our solar system. And with the development of Curiosity’s precise landing system, we can finally reach the mysterious parts of the planet. But it’s these areas that require a craft sterilization process.
In the 1970s Vikings 1 and 2 revealed what seemed like a dead planet, so planetary-protection requirements were relaxed. Now, with more knowledge of Mars’ environment, missions set to visit areas with evidence of flowing water below the surface have to meet the strict-and more costly- Vikings standards.
Finally, there’s the philosophical problem of what responsibility, if any, we have to other planets and any life we leave there. The truth is we’re never going to be able to fully protect Mars if we intend to explore it. And spreading is simply what life does.
“If we want to survive for a long time, we have to expand beyond Earth,” Schulze-Makuch says. “There’s no other way.”
43. Strict spacecraft sterilization procedures are meant to ______.
A.decrease the costs of space exploration |
B.help the search for life forms beyond Earth |
C.contribute to innovative missions in the universe |
D.prevent Earth life being transferred to other planets |
44. Planetary-protection requirements were relaxed in the 1970s because ______.
A.there was no preclse landing system |
B.Mars was considered to be a lifeless planet |
C.the mysterious parts of Mars remained unknown |
D.flowing water was found below the surface of Mars |
45. Dirk Schulze-Makuch and Alberto Fairen are most likely to agree that ______
A.Mars is now on the edge of being destroyed |
B.human beings are too ambitious to expand beyond Earth |
C.there is no need to worry about bringing Earth life to Mars |
D.we need to be responsible for keeping Mars what it is like now |
46. Schulze-Makuch takes a(n)______attitude towards planetary protection.
A.optimistic | B.relaxed | C.debatable | D.negative |