Europa has an ocean hidden beneath a thick shell of ice and has long has been viewed as a potential habitat for life, alongside Mars and Saturn’s moon Enceladus.
With more than 28,000 essays submitted, one winner will get to watch the launch live from Cape Canaveral.
It is most torrid environments on the planet with daily temperatures in winter exceeding 45 degrees Celsius.
It might be possible for bacteria to feed on electricity and carbon dioxide to produce value-added compounds like biofuels.
Microbes react very quickly — within five to seven years — to even slight changes in the climate.
A tropical forest five times the size of England, some 600,000 square kilometres, has been destroyed since 2014.
They announced their discovery of microbes in the subglacial lake in 2013, receiving worldwide attention.
The fracture, which occurred near the shield's outer edge and spans the circumference of the component, was discovered by NASA on April 12.
New data from the Curiosity rover forms the basis of a theory that the Gale crater had been home to a lake with conditions suitable for life.
Grains of rock spewed into deep space suggest a small moon of Saturn has hydrothermal vents, boosting theories it may harbour microbial life.