‘First tree on Mars’: Scientists measure the greenhouse effect needed to terraform the Red Planet

How much greenhouse warming would be needed to warm the cold climate of Mars enough to allow trees to grow on the Red Planet?

A new study shows just how much carbon dioxide (CO2) emissions into the atmosphere need to be increased. Mars keep plants growing, raise the planet’s temperature just enough to allow trees to grow.

Surprisingly, the conditions that would allow plants to grow on the Red Planet do not first occur in the “tropics” of the planet.

Energy balance

This futuristic plant-growing scenario is led by Robert Olszewski, a professor at the Warsaw University of Technology in Poland. He and his colleagues studied the surface energy balance of Mars, such as the diffusive heat exchange between condensation and evaporation of carbon dioxide, heat exchange with the subsurface, and heat transfer by atmospheric circulation.

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Map of Mars with shaded tropics. Given enough greenhouse warming, the first tree on Mars will grow outside the tropics in the Hellas basin.

Map of Mars with shaded tropics (±25°). Given enough greenhouse warming, the first tree on Mars will grow outside the tropics in the Hellas basin. (Image credit: Mars Orbiter Laser Altimeter (MOLA) data/Olszewski et al.)

“Surprisingly, the conditions that allow plants to grow do not first arise in the tropics (±25°), but in the region of the Hellas basin. greenhouse effect expands the area suitable for plant growth in the southern hemisphere,” explains the new research paper.

Using temperature and pressure data sets from the Viking Mars lander collected in the 1970s, Olszewski and members of the research team modeled various processes on Mars, both currently and in past/future eras.

The Viking lander was the first mission to successfully land on Mars and conduct chemical analysis of its surface.

NASA’s Viking missions to Mars, 1970s. (Image credit: NASA)

“Here we use a basic model to study the greenhouse effect caused by increasing CO2 emissions and man-made greenhouse warming,” Olszewski notes in a paper presented atAstrobiology and the Future of Life,” held recently at the Lunar and Planetary Institute in Houston, Texas.

Pressure cooker

Olszewski and his colleagues estimated the required total pressure on Mars, the high percentage of acceptable CO2, the amount of O2 required, the amount of water available, and the temperature range required for tree growth.

A huge canyon can be seen on the surface of Mars. Valles Marineris, a mosaic of the Mars hemisphere, consisting of 102 images of this enormous object on the Red Planet, taken by the Viking orbiter.

Valles Marineris, a mosaic of the Mars hemisphere, consisting of 102 images of this enormous object on the Red Planet, taken by the Viking orbiter. (Image credit: NASA/USGS/Viking Project)

The atmospheric conditions existing on Mars today make the existence of life impossible,” Olszewski points out. “Plant growth requirements on Mars have been considered in the context of terraforming and low-pressure greenhouses.”

The study focused on temperature “because it is a fundamental environmental variable that changes during terraforming and controls the CO2 cycle and liquid water formation,” Olszewski adds. Oxygen levels in a dense and warm atmosphere remain an important issue in their own right.

Growing season

“Based on temperature, it should be several tens of degrees higher, while daily fluctuations should be much lower. For trees to grow, the growing season should last at least 110 sols (Martian days),” studies show that the given minimum temperature, average temperature and maximum temperature that can be reached on the Red Planet.

Olshevsky and his colleagues note that on Earth the highest tree lines are mostly found in the tropics, but they depend on the location of the thermal equator. “Thus, the equatorial regions of Mars can be expected to be where the first tree appears.”

An artist's illustration of Mars being terraformed into a world more like Earth.

A future Mars, protected from direct solar wind, would reach a new equilibrium allowing a vast atmosphere to support liquid water on its surface. (Image credit: Dain Ballard, CC BY-SA)

But due to the relatively large eccentricity of Mars’ orbit, the southern hemisphere, where in summer about perihelionhas relatively warm summers, the researchers note. In addition, the orbital period of Mars is 1.9 Earth years.

Thus, the long, warm southern summer provides the first growing season suitable for trees,” reports Olszewski. “In particular, we find that the low elevation of the Hellas basin allows for the first conditions favorable for tree growth,” the researchers conclude.

‘First tree on Mars’: Scientists measure the greenhouse effect needed to terraform the Red Planet

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