Fifty years ago, NASA's Viking landers made humanity's first attempt to find life on Mars — and came up empty. Today the evidence is piling up: Perseverance has drilled into a rock covered in "leopard spots," Curiosity has pulled 21 organic molecules from ancient mudstone, and a September paper confirmed that Jezero Crater experienced three distinct episodes of water activity. But just as the clues converge, Congress has killed the plan to bring Mars samples home — the titanium tubes holding potential traces of life will stay where they are.
On July 20, 1976, Viking 1 became the first spacecraft to operate on the Martian surface; Viking 2 followed in September. Their robotic arms scooped up soil for the first extraterrestrial life-detection mission: nutrient-broth gas tests, nutrients tagged with radioactive carbon-14, and heated-soil carbon-uptake tests. The first two returned signals that looked like metabolism, but the mass spectrometer found essentially no organics, and most biologists lost interest.
It took until 2008, when the Phoenix lander found perchlorate salts in Martian soil, and 2010, when lab work showed perchlorates destroy organics when heated, for a likely explanation to emerge: Viking's heating step may have burned up exactly what it was looking for. In 2014, Curiosity finally found organic molecules locked in Martian rock.
In July 2024, Perseverance drilled a rock named "Cheyava Falls" in Jezero Crater. Its surface is covered in leopard-like spots rimmed with iron phosphate and iron sulfate — on Earth, similar textures often result from chemistry involving microbes. A September 2025 *Nature* paper led NASA to call it a "potential biosignature."
The core was sealed in a titanium tube. Then-NASA administrator Sean Duffy called it "the closest we have ever come to discovering life on Mars." But NASA stresses a non-biological origin still can't be ruled out — certainty requires bringing the rock to an Earth laboratory.
On September 21, 2026, a Purdue-led study in *Communications Earth & Environment* reconstructed a far more complex water history for Jezero's "Margin Unit": over 185 bedrock targets analyzed with Perseverance's SuperCam across about 265 meters of elevation.
Instead of the expected ancient-lakeshore sedimentary rock, the team found olivine-rich igneous rock altered by water three times: carbon-dioxide-rich groundwater reacting with olivine to leave carbonate ridges in fractures; lake or groundwater leaving silica behind; and later hot fluids surging through new fractures, forming calcium-sulfate and fluorite veins up to 25 centimeters thick.
The study doesn't prove Mars ever hosted life, but it makes the Margin Unit a priority target for sample return.
This past summer, NASA Goddard's Instrument Field Team traveled to the Bay of Stoer in the Scottish Highlands. The Stoer formation, laid down about 1.2 billion years ago, preserves evidence of microbial activity from before land plants existed; its gray-green "reduction spots" are sometimes traces of ancient microbes interacting with rock.
Those spots are exactly what Perseverance found in Jezero. Rocks that both resemble ancient Martian lake-and-river environments and preserve microbial evidence are vanishingly rare on Earth. The team collected samples from cliffs with 11-to-15-foot tidal swings for analysis in U.S. labs; a September 29 NASA blog post said follow-on work would help plan new rover investigations and prepare for future sample analysis.
In April 2026, *Nature Communications* reported that Curiosity's first TMAH experiment — an extraction method that doesn't destroy organics — found 21 organic molecules in 3.5-billion-year-old lakebed mudstone in Gale Crater, seven of them never before seen on Mars. In February, a French team reported decane, undecane and dodecane — the longest carbon chains ever found on Mars, possible fragments of fatty acids — in a reanalysis of mudstone drilled in 2013.
"Mars has always allured us, even when it's been disappointing," said Ashwin Vasavada, Curiosity's project scientist at JPL. "The whole history of Mars exploration is a big roller coaster."
But the road home is blocked. Mars Sample Return began facing budget cuts in March 2024; the January 2026 compromise spending bill states it "does not support the existing Mars Sample Return program." The White House had called it "grossly overbudget," with projections exceeding $11 billion and a return no earlier than 2040. "We have not abandoned bringing samples from Perseverance back," Mars Exploration Program Director Tiffany Morgan said in April. "We've spent 50 years preparing to get these samples back," said Arizona State's Philip Christensen. "Now we're two feet from the finish line — oh, sorry, we're not going to complete the job."
Europe's Rosalind Franklin rover has had a tortured path: crates packed, then Russia's invasion of Ukraine killed the partnership. NASA rejoined in 2024; the 2026 Trump budget threatened another exit, but Congress rejected it and awarded the launch contract to SpaceX. If all goes well, it will touch down in 2030 at Oxia Planum — 4-billion-year-old rocks rich in phyllosilicate clays, possibly the shoreline of an ancient ocean. Its MOMA instrument can extract organics with a laser without activating destructive perchlorates.
China's Tianwen-3 is accelerating too: the landing search has narrowed to eight candidate sites, with a final selection expected before the end of 2026 and launch in late 2028, aiming to return Mars samples to Earth.
Half a century ago, Carl Sagan wrote that life on Mars was "not only possible; it may be favored." If Mars truly hosted life — and if Earth's life shares its lineage — then Martian microbes would be the ancient ancestors of everything alive, humans included. This fifty-year hunt is only now entering deep water.