We’re finally ready to know: is there life on Mars?

Written by Ethan Siegel

“They say once you grow crops somewhere, you have officially ‘colonized’ it. So technically, I colonized Mars. In your face, Neil Armstrong!” –Andy Weir

In 1960, just three years after Sputnik 1, humans began launching missions to Mars.

A composite of multiple images from the Mariner 4 mission, the first spacecraft to ever successfully fly to and image Mars. Image credit: NASA / Mariner 4.

After six USSR and USA failures, Mariner 4 successfully flew by Mars in 1965, sending back 21 photos.

The same year that humans first walked on the Moon, 1969, Mariner 6 and 7 returned images like these of Mars, showing a cratered, lunar-like surface. In the 1960s, there was no way to know how rich Mars’ surface truly was. Image credit: NASA / Mariner 7.

NASA’s Mariner 6 and 7 also reached Mars, along with the USSR’s Mars 2 and 3, showing a heavily cratered, Moon-like surface.

A dust storm on Mars, a common occurrence during the Martian summers. These storms were first discovered by the Mariner 9 mission in 1971. Image credit: NASA/JPL-Caltech/MSSS, from Mars Reconnaissance Orbiter.

Mariner 9 arrived at Mars in 1971, however, orbiting it for over a year and changing our view of it forever.

Valles Marineris, seen at an angle of 45 degrees to the surface in near-true colour and with four times vertical exaggeration. It is the largest canyon on any planet in the Solar System, more than three times the extent of Earth Grand Canyon. Image credit: ESA/DLR/FU Berlin (G. Neukum).

Mars contained dust storms, extinct volcanoes, and the largest chasm ever discovered on a planet: Valles Marineris.

The first truly successful landers, Viking 1 and 2, returned data and images for years, including providing controversial signals for life on the red planet. Image credit: NASA and Roel van der Hoorn.

NASA’s Viking landers, in 1976, returned the first color photos from the surface.

Landing on the Martian surface in July of 1976, this July 24 picture of Mars is, iconically, one of the very first images of the Martian surface as it would appear to human eyes. Image credit: NASA / Viking 1.

In addition, they tested for signs of life, discovering some evidence for organic materials, but nothing definitive.

These tendrils are evidence of water flowing down a slope and into a massive river. Images like this, from Mars Odyssey, cover the entire Martian globe. Image credit: NASA / JPL-Caltech / University of Arizona, Mars Odyssey / THEMIS.

Subsequent orbiters allowed us to map out the entire surface in high resolution; we now have a global map.

These dunes, from are inside Endurance Crater on Mars, were some of the features discovered by the first and second generation of rovers on Mars. Image credit: Mars — Opportunity Rover NASA/JPL Caltech/Michael Benson/Kinetikon Pictures.

Meanwhile, landers, orbiters and rovers continued, becoming more advanced and discovering evidence for liquid water.

A color-enhanced view inside Newton Crater, showing the recurring slope lineae, which provide the strongest evidence for flowing liquid water on the Martian surface today. Image credit: NASA/JPL-Caltech/Univ. of Arizona / Mars Reconnaissance Orbiter.

Most excitingly, methane vents and flowing surface features point towards past — and possibly present — microbial life.

Relic microbes revealed by a scanning electron microscope in the ALH84001 meteorite, which originated on Mars. It is unknown whether the microbes are of Martian origin or not. Image credit: NASA, 1996.

Two upcoming landers, ESA’s ExoMars Rover and NASA’s Mars 2020, will seek advanced biosignatures and unambiguous life signs.

Most recently, the Mars Curiosity rover detected Methane vents on Mars, which could have been produced either organically or inorganically. If it’s organics, I will lose a bet with physicist Robert Garisto! Image credit: NASA/JPL-Caltech/SAM-GSFC/Univ. of Michigan.

After 50+ years, we’re ready to know.

Read more at medium.com