A major US research body has warned that cuts in Nasa's 2006 budget will hamper progress in understanding our planet and the rest of the Universe.
Nasa aims to return humans to the Moon
The American Geophysical Union says there are signs space and Earth science have dropped in priority at Nasa.
The AGU says research in these areas is threatened by the financial demands of meeting President Bush's Moon-to-Mars initiative and other manned programmes.
It also says Nasa is doing "more than it can with the resources provided".
"The problem is that Nasa has a great deal on its plate," said Eric Barron, who has chaired an AGU Panel on President Bush's Moon-to-Mars vision for space exploration.
"[It] wants to return the space shuttle to flight, finish the space station, [build] the next generation of space transport vehicles as well as exploring the Moon and Mars with humans," Dr Barron told reporters at a news conference in Washington DC.
Nasa's proposed 2006 budget would reduce science research by about $1.2bn over the next five years.
The AGU said it was particularly concerned about several Earth System Pathfinder missions and Explorer-class satellite missions, which have been eliminated or subjected to prolonged delays.
"These are the smaller, less expensive, flexible, innovative mechanisms that provide frequent access to space," said Dr Barron.
The AGU position statement - Nasa: Earth and Space Sciences at Risk - says these losses will detrimentally affect weather forecasting, search and rescue, disaster planning and Solar System exploration.
When Nasa announced its proposed 2006 budget in February, it reaffirmed the space agency would continue to be guided by President Bush's vision for space exploration.
This vision, outlined in January 2004, has included a major shift in emphasis towards human exploration, with the intention of returning astronauts to the Moon and, possibly, taking them on to Mars.
The AGU releases a position statement roughly every year.
A Nasa spokesperson was unable to comment on the AGU statement at the time of writing.