Without including a price tag for his initiative, a Texas congressman filed legislation Wednesday that would set NASA on a course to reach Mars with human explorers within 20 years. U.S. Rep. Nick Lampson, a Beaumont Democrat whose legislative district includes NASA’s Johnson Space Center in Houston, said his bill, “The Space Exploration Act of 2002,” is intended to give new focus to the financially troubled U.S. space program. Lampson’s bill would establish a new office of exploration within NASA funded at $50 million in 2003 and $200 million in 2004. But the lawmaker does not attempt to calculate how much it would cost to send human explorers to Mars. He leaves that task to the experts who would staff NASA’s new exploration organization.