In an effort to spur big science discoveries, the U.S. government and private groups have started offering cash prizes. Some examples:

$25 million
Name: Virgin Earth Challenge
Goal: A system that can remove greenhouse gases from the air for 10 years or more and that is eco-friendly.
From: Al Gore and Richard Branson

$10 million
Name: NewOrgan Prize
Goal: To use regenerative medicine to grow a new organ and to transplant that organ into a patient and have it function for at least two years by 2020.
From: Methuselah Foundation

$2 million
Name: DARPA Urban Challenge
Goal: Develop and drive fully autonomous vehicles in a long-distance competition. (It was awarded in 2007.)
From: Department of Defense

$1.5 million
Name: Sample Return Robot Challenge
Goal: Build a rough-terrain robot capable of finding and retrieving geologic samples.
From: NASA and Worcester Polytechnic Institute

$1.35 million
Name: Green Flight Challenge
Goal: Build an aircraft that can fly 200 miles on a gallon of gasoline per passenger. (It was awarded in 2011.)
From: NASA, CAFE Foundation and Google

$1 million
Name: PETA prize
Goal: Develop a way to grow and manufacture in vitro chicken meat that tastes just like real chicken.
From: People for the Ethical Treatment of Animals