The European Space Agency says its flagship Mars mission will lose a major instrument package to contain costs, BBC reported.
The Exomars venture will launch a rover to the Red Planet in 2016, to search for signs of past or present life.
It was hoped a static science payload called Humboldt could also be put on the surface to study the weather and, for example, listen for "Marsquakes".
But agency officials announced at the Paris air show that financial constraints now made this impossible.
Esa director-general Jean-Jacques Dordain said de-scoping ExoMars would also give extra margin to engineers who were concerned that the rover's design was pushing the limit of the maximum possible mass for mission.
Mr Dordain said the loss of Humboldt was inevitable given the promise he had made to European governments in November last year to keep the cost of the project as close as possible to 850m euros.
He said it was also likely now that the US would play a significant role in the endeavour, further limiting the financial burden on European taxpayers.
The American space agency (Nasa) has its own money worries and is keen to share the cost of Mars exploration with Europe.
Nasa is set to sign a "letter of intent" to this effect at a bilateral meeting in Plymouth, UK, on 30 June.
This would mean all future Red Planet missions being badged Nasa/Esa projects.
On ExoMars, the US is now set to provide the launcher - an Atlas rocket. It will also probably build the carrier spacecraft that delivers the rover to Red Planet; and the orbiter which will circle above Mars and relay its data back to Earth.
This would represent a considerable investment on the part of the Americans, but the quid pro quo is that European money will then be put into future US-led missions.
Humboldt's omission from ExoMars will be a bitter blow to its scientists.
It was intended to study the surface environment and the geophysics of the deep interior.
Its sensors were being designed to undertake - among other things - meteorological investigations and an assessment of the radiation conditions on Mars.
Seismometers would have revealed remarkable new insights into the nature of Mars' geological structure.
Esa's science director, David Southwood, told the BBC he was confident that Humboldt would eventually fly to Mars, perhaps as part of a network of static stations planted around the planet.
He said the science it would deliver was a necessary first step towards the agency's eventual goal of sending a mission to planet that could fetch rocks back to Earth for detailed study.