An Ancient ‘Smiley Face’ on Mars May Hold Info About Martian Life

A patch of textured ground with a circular pattern resembling a smiley face. The raised areas form two dots for eyes and a curve for a mouth, with the entire shape outlined in a slightly lighter hue.
This infrared image of the Martian surface shows a smiling chloride deposit, which may indicate ancient life on Mars. | ESA/TGO/CaSSIS

Despite being harsh and inhospitable, Mars has a surprisingly cheery disposition. Scientists have located a “smiley face” on the Martian surface as part of a new study of the Red Planet’s surface.

The smiley face-like structure, which as Space reports is only visible in specific situations, is the remains of an ancient Martian lake that scientists believe dried up billions of years ago.

“Once a world of rivers, lakes, and possibly oceans, Mars now reveals its secrets through chloride salt deposits found by our ExoMars Trace Gas Orbiter,” explains the European Space Agency (ESA) on Instagram. “These deposits, remnants of ancient water bodies, could indicate habitable zones from billions of years ago.”

“The discovery of nearly a thousand potential sites offers new insights into Mars’ climate and potential for past life.”

Aerial view of a Martian landscape featuring several impact craters of varying sizes. The surface has a rugged, ridged texture with streaks of blue-tinted material. The largest crater is near the top left corner, showing a smoother basin in the center.

A high-resolution image of the Moon's surface showing various craters of different sizes. The terrain appears rugged, with a large, prominent, white-colored crater at the lower right side, contrasting with the darker, greenish surrounding areas.

In space since 2016, the ExoMars Trace Gas Orbiter is a joint mission between the ESA and Roscosmos. The mission’s primary objective is to “gain a better understanding of methane and other atmospheric gases that are present in small concentrations (less than 1% of the atmosphere) but nevertheless could be evidence for possible biological or geological activity.”

An artist's impression of the ExoMars Trace Gas Orbiter spacecraft separating from its entry, descent, and landing demonstrator module, Schiaparelli, with the planet Mars in the background. The module and spacecraft are depicted in space near the reddish planet.
Artist’s impression depicting the separation of the ExoMars 2016 entry, descent and landing demonstrator module, named Schiaparelli, from the Trace Gas Orbiter, and heading for Mars. | ESA / ATG medialab

The new ancient smiley face is not the first the ESA has imaged on the Martian surface. Crater Galle, named for the German astronomer J.G. Galle (1812-1910) is informally called the “happy face” crater, and was first seen by NASA’s Viking Orbiter 1 mission. The ESA’s High-Resolution Stereo Camera (HRSC) aboard the Mars Express spacecraft took a detailed look at the crater in 2006.

A high-resolution image of Galle Crater on Mars, depicted in false color. The crater has a distinctive circular formation with varying shades of purple, blue, and green, highlighting terrain features. Jagged ridges and smooth plains are visible within and around the crater.
This false-color mosaic of Crater Galle was derived from three HRSC color and nadir channels gathered during five overlapping orbits. | Credit: ESA/DLR/FU Berlin (G. Neukum)

The new smiling face deposit is detailed in research published in Nature‘s Scientific Data journal last month.

Map of Mars showing the estimated chloride candidate sizes, marked with circles of varying sizes and colors, overlaid on a topographic elevation map. Below is a hexbin plot indicating image density from both N (northern) and S (southern) hemispheres based on latitude.
The distribution of potential chloride-bearing deposits on Mars as identified by CaSSIS. Top: Global distribution of all CaSSIS-derived chloride candidates (shades of violet); color indicates the estimated size of the respective candidate; white/black crosses mark the locations of THEMIS-/OMEGA-derived chloride deposits/hydrous mineral detections; Viking Merged Color Mosaic in the background. Note mark for the location of Fig. 1 (black circle). Bottom: coverage heatmap (hexmap) of CaSSIS image density including orbit number 27,816, 02/17/2024.

“Chloride deposits are markers for early Mars’ aqueous past, with important implications for our understanding of the martian climate and habitability,” the researchers explain. “The Color and Stereo Surface Imaging System (CaSSIS) onboard ESA’s Trace Gas Orbiter provides high-resolution color-infrared images, enabling a planet-wide search for (small) potentially chloride-bearing deposits.”


Image credits: ESA/TGO/CaSSIS

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