"Decane, undecane, and dodecane were detected in a Martian sample" from the paper at PNAS: https://www.pnas.org/doi/abs/10.1073/pnas.2420580122.

A NASA article: https://www.jpl.nasa.gov/news/nasas-curiosity-rover-detects-...

Science article: https://www.science.org/content/blog-post/alkanes-mars: So why didn't these newly announced larger molecules show up then?

That's because this time the samples got a different treatment (two cycles of strong heating) before the mass spec analysis.