NASA's complicated future on Mars

• Since the 1960s, the space agency has sent about 20 spacecraft to Mars, mapping the world from orbit and learning more about it from the ground with rovers and landers.

Driving the news: The Mars Sample Return mission — a joint project between NASA and the European Space Agency — is currently under a major review.

• A report from Ars Technica last month revealed the cost of the mission may have increased from $4 billion or $5 billion to $8 billion or $9 billion, according to one estimate.
• NASA confirmed to Axios that one estimate in the review of the program was in that cost range, but added, "all scenarios are highly speculative."
• "The agency aims to set its baseline cost and schedule commitment for the Mars Sample Return Program later this year as part of the confirmation review process," NASA added.
• "It's more uncertainty than I've seen with other big missions," John Logsdon, founder of the Space Policy Institute at George Washington University, tells Axios. The review will "presumably set the course for the rest of the mission," he says.

Between the lines: If the sample return mission does come with a higher price tag, it could impact NASA's entire planetary science portfolio, as other missions are experiencing technical delays and schedule problems.

• The space agency was recently forced to indefinitely delay the VERITAS mission to Venus due to other missions needing to be prioritized first.
• The Psyche mission to a metallic asteroid is expected to launch in October, after it was delayed last year due to software issues.
• And the NEO Surveyor mission to find dangerous asteroids near Earth — which was marked as a high priority by Congress — has increased in cost, going from about $600 million to $1.2 billion.

The intrigue: NASA has already invested heavily in sample return through another mission — the Perseverance rover — that laid the groundwork for it.

• NASA built Perseverance around the idea that it would cache samples that would eventually be retrieved by a sample return mission and brought back to Earth.
• Perseverance has already collected and stored a number of samples that could hold signs of past life, but scientists won't be able to analyze them until they are returned to Earth.

The big picture: Cost growth for major NASA missions isn't new. NASA's James Webb Space Telescope increased in cost by billions of dollars before its launch, earning the nickname "the telescope that ate astronomy."

• But the Mars Sample Return mission is far more limited in scope than JWST, which could mean it garners less support among the broader space science community.
• "JWST is a platform for science for decades, and that makes the coalition behind it much more durable from a scientific perspective," the Planetary Society's Casey Dreier tells Axios.

What to watch: Congressional support for the mission will also likely be crucial going forward, especially if the cost of the mission increases significantly.

• But the mission budget isn't set in stone, and it's possible NASA will adjust the design of the mission or how it is built in order to find some cost savings.

The bottom line: If the Mars Sample Return mission doesn't go forward, it would effectively leave a job unfinished on Mars, experts warn.

• "There's something very sad to me about the image of these carefully, lovingly collected and curated precious samples of the Martian surface prepared by the Perseverance rover just functionally rotting on the surface of another planet for all eternity," Dreier said.