I think the argument for the ExoMars participation is largely political. We (Obama) stiffed them hard in 2012, as I said; and after the Ukraine War forced them to hit the ejector seat on Roscosmos, they were in a tough spot, and it is probably fairly cheap diplomacy to help ’em.

Not that ExoMars won’t produce worthwhile science (it should); but I don’t think that was the sole motivation for NASA. Also, it will end up going to a location that is sure to retain Cat IVb classification (i.e., no Starships).

To maximize that probability, though, means keeping NASA involvement as minimal as possible – most preferably zero – as NASA involvement always introduces delays.

VSECOTSPE had a thoughtful idea on this a few months back. If Trump really wants a “sanctioned” SpaceX venture to Mars before he leaves office, have NASA issue a Space Act RFP for a cargo demonstration to the Martian surface, to launch by the 2028 launch window, with some appropriate minimum payload requirement (50 tons or whatever) with mission architecture and design left entirely to the bidder, for a nominal award and use of the DSN; let their boffins cook up whatever science packages they want to stick on it, with an understanding of the risk involved. It wouldn’t put lives at risk, and it would allow a NASA involvement that is minimally intrusive, while still giving Trump something to crow about.

But I think that while the future of ExoMars is most likely to be unconnected budgetarily to whatever Elon plans to do anent Mars, its overall fate will still be influenced by whatever he manages to do between now and 2026. Elon seems pretty eager to put the pedal to the metal on his Mars efforts, but the notion of sending at least one – and possibly several – cargo-only Starships, crewed by Optimus robots, to Mars in 2026 is still, in my view, a project with a probability above 50% of proving doable. To maximize that probability, though, means keeping NASA involvement as minimal as possible – most preferably zero – as NASA involvement always introduces delays. If there is no NASA money/involvement in SpaceX’s initial Mars efforts then there can be no adverse budgetary impact on any NASA decision anent ExoMars.

That said, it remains an open question as to how much actual incremental science value there is to be had from ExoMars as opposed to a project of some other kind costing the same amount of NASA cash. Given the new target departure date for ExoMars, the answer to this question certainly could prove to be heavily influenced by whether or not Elon actually gets off a 2026 Mars maiden effort. If he does, that would presage a far larger effort in the 2028-9 window that might even include human crew. Even just a larger Optimus-crewed effort then – or an initial one if 2026 proves a miss – would raise serious questions about ExoMars’s cost-effectiveness, especially if Curiosity and Perseverance are both still chugging along.

Eric opines: “The Trump administration is poised to push NASA’s exploration program to focus on Mars, and that will likely entail sending SpaceX Starships to the red planet with increasing frequency. SpaceX is aiming for the 2026 launch window for Mars and certainly will be targeting one or more Starships for late 2028. Will NASA, citing redundancy with Starship missions, pull the plug on ExoMars again? With ExoMars, the only certainty is to expect the unexpected.”
https://arstechnica.com/space/2025/03/four-different-rockets-three-landers-and-two-decades-will-exomars-ever-launch/

Berger is increasingly hostile to the administration and Elon’s involvement with it (check out his BlueSky feed, where he clearly feels more uninhibited) but maybe it’s not *totally* paranoid to wonder about NASA’s funding commitment to ExoMars. After all, it was the Obama Administration pulling out of it abruptly in 2012 that left ESA holding the bag the first time around — we’ve been to this rodeo before. But Jared Isaacman gets a vote, and given some of his past comments I would be very surprised if he would be happy seeing this modest commitment deep-sixed.