For more than half a century, Americaโ€™s space program has captivated the worldโ€™s imagination while expanding the frontiers of knowledge and engineering. As we face the first prolonged gap since the 1970s in our ability to launch humans into space, heightened attention will be focused on space science, and especially planetary science, which has delivered a series of dazzling missions that have begun to yield answers to profound questions about our place in the cosmos.

NASA science has succeeded when it has maintained a balanced portfolio committed to strong partnerships with universities and its national centers and laboratories โ€” allowing each discipline to plan missions and nurturing successive generations of scientists. The space spectaculars of the past 15 years were the result of two decades of investment.

President Barack Obamaโ€™s proposed NASA budget would dramatically cut funding for planetary science, and with it, groundbreaking missions to Mars and outer planetary bodies like Jupiterโ€™s icy moon, Europa. Congress committed our nation to carry out these missions by including a provision in last yearโ€™s appropriations bill requiring NASA to fund and fly the top priority missions recommended by the National Academy of Sciencesโ€™ decadal survey, which has always been a roadmap for NASAโ€™s planetary program.

This nation must set priorities and make difficult choices if we are to maintain our scientific leadership in an age of fiscal austerity. But even as we struggle to set America on a more fiscally responsible path, we must invest in those scientific and technological endeavors that promise the greatest return. Americaโ€™s unique expertise in designing and flying deep-space missions is a priceless asset. NASAโ€™s missions to our planetary neighbors have always provided an enormous return on investment by advancing modern technical marvels like digital photography, cellular communications and advanced robotics. The technologies required for these missions help keep America on the leading edge of innovation. Investments in planetary programs preserve and expand the nationโ€™s unique skills in entry, descent and landing on another planet, a vital precursor to NASAโ€™s long-term strategy of sending astronauts out into the solar system.

The presidentโ€™s 2013 budget makes important investments in cutting-edge space technologies that will fund important missions such as the James Webb Space Telescope and new launch systems for our manned space program. But without congressional action, the administrationโ€™s cuts to planetary science would devastate Americaโ€™s planetary program.

The robotic Mars program, one of our nationโ€™s science jewels, faces the most severe cuts, including a rover mission to Mars in 2018 identified as the highest priority in planetary science in the most recent decadal survey. This would be a tragic loss for a program that has made major scientific discoveries and captured the interest of people around the world. In the three days after the Mars Spirit rover landed in 2004, the missionโ€™s website received nearly 1 billion hits. NASA still operates Spiritโ€™s twin, Opportunity, almost eight years beyond its expected lifetime, and is preparing for the landing of the most ambitious surface explorer ever sent to another planet โ€” the Mars Science Laboratory Curiosity, which is due to touch down on Aug. 6.

Another of the decadal surveyโ€™s top priorities is a mission to Europa, which is thought to have saltwater oceans 10 times deeper and far larger than Earthโ€™s. Europaโ€™s icy crust also shows evidence of volcanic hot spots on the sea bed created by tidal flexing as the moon orbits in Jupiterโ€™s immense gravity field. A huge saltwater ocean that has been oxygenated for eons combined with endless heat sources on the sea bed create ideal conditions for life forms like those we have discovered near undersea volcanic vents at the mid-ocean ridges here on Earth. Congress must prevent this vital mission from being shelved.

The excitement of these missions to Mars and Europa will motivate a new generation of American students to choose technical careers โ€” essential to the nationโ€™s economic well-being and our national security. As the Congress and the president work to resolve our budgetary challenges, we cannot forget that todayโ€™s decisions will have consequences far beyond the Mars and Europa missions. If the nationโ€™s young people are not attracted to science and technology, NASAโ€™s overall capabilities will be severely diminished and our competitiveness undermined. The administrationโ€™s proposal would compromise a program painstakingly built up over decades and jeopardize a work force that, once dissolved, would be difficult, if not impossible, to reconstitute.

Slashing NASAโ€™s budget for exploring the solar system would be a serious mistake that would threaten our nationโ€™s hard-won and long-held leadership role, and would come at a terrible time, now that China and other nations are rising to challenge American primacy in space. Meeting that test is good for science and good for America; by exploring other worlds, we remain competitive on our own.

U.S. Reps. Adam B. Schiff (D-Calif.) and John A. Culberson (R-Texas) serve on the House Appropriations Subcommittee on Commerce, Justice, Science, and Related Agencies.