NASA’s September 28, 2015 announcement of liquid water on Mars captivated the world and rekindled hopes for finding extraterrestrial life in our solar system.

The Announcement

“Mars is not the dry, arid planet we thought of in the past,” NASA declared, revealing dark streaks (recurring slope lineae) on crater walls were flowing briny water. The Mars Reconnaissance Orbiter detected hydrated salts - definitive evidence of liquid water during warm seasons.

Media Frenzy

The revelation trended #1 globally for days. Matt Damon’s “The Martian” premiered the same week - perfect timing. NASA’s press conference drew record viewership. President Obama tweeted excitement. The discovery answered a question humans wondered for centuries: is there water on Mars?

The Reality Check

The “flowing water” exists as thin brines, extremely salty to remain liquid in Mars’ cold, low-pressure environment. Volumes are tiny - not lakes or rivers. Later studies suggested some lineae might be flowing sand, not water. Still, periodic liquid water means potential habitats for microbial life.

Implications

The discovery influenced Mars 2020 Perseverance landing site selection. NASA’s “follow the water” strategy guides astrobiology missions. If life exists on Mars, it likely thrives in briny subsurface environments, not on the radiation-blasted surface.

Underground Lakes

In 2018, radar detected a 12-mile-wide lake beneath Mars’ south polar ice cap, 1 mile underground. Likely super-salty and near freezing, but stable liquid water. Multiple subglacial lakes now suspected. The search shifted from “was there ever water?” to “where is the water now?”

Source: NASA Mars Water Announcement