You can't squeeze blood from a turnip ( 萝卜) , and(1)you can't squeezewater from moon rocks, either. A new analysis of samples(2)by the Apolloastronauts suggests that there is virtually no chance that water ever existed beneaththe lunar ( 月球的 )(3).
Scientists have been(4)for decades about whether the moon containssignificant quantities of water. Theoretically, it should because the moon was oncepart of Earth--the moon was(5)by a disastrous collision between our planetand a Mars-size body over 4 billion years ago. Yet(6)chemical analyses in the1970s and '80s of rocks that had been brought back by the Apollo missions turnedup virtually no evidence of lunar water. More recently, using improved(7)toexamine the molecular constituents ( 分子构成) of the rocks, researchers havefound a very small amount of hydrogen ( 氢) --an indicator of water. In 2013,scientists also found evidence of water ice on the surface of the moon, but wheredid that ice come from was unclear. It was even(8)deposited by an ancientcomet impact. It's an important riddle ( 谜 ) to solve, as researchers would liketo use lunar water to(9)rocket fuel for future deep-space missions.
A team has(10)to solve the mystery. Recently, the researchers reportedonline in Science that the moon has basically zero subsurface water.
While eco-minded chefs dishing up1mushrooms, the average Americanmeal travels around(1),500 miles from farm to table. In the US, processing, packaging,transporting, storing and preparing fruit and vegetables requires about four times asmuch(2)as growing them in the first place. And around the world, up to a third offresh food spoils in transit.
The problem is that while the countryside is a great place to grow plants,with(3)water, free sunlight and fertilizer from livestock ( 家畜，牲畜) , fewerand fewer people are living there. Over half the world now lives in cities, a proportionthat will rise to 70% by 2050. If tomorrow's(4)centres are not to go hungry, theywill(5)need to produce much more of the food their dwellers ( 居民 ) consume.
At M1T in Cambridge, Massachusetts, two groups are(6)the problem fromdifferent directions. However, both MIT technologies are focusing on crops that areexpensive in(7), small and easy to grow. And although LEDs and digital sensors arebecoming more(8), neither system can compete on cost with traditional agriculture.
"If you're really going to try to sell tomatoes, you have to compete with the guyswith hectares ( 公顷) under cultivation in Mexico and California," says Mr. Haper,CityFarm's founder. "That's where we're all(9)and no one can do it yet. Thetechnology to compete with(10)methods is still five or ten years away."