How long does it take to orbit Mars? The answer is not certain!

(Image credit: Nissian Hughes/Getty Images)

Humanity has had a long-standing fascination with Mars, and NASA has ambitious plans to send astronauts to the Red Planet in the coming decades. Anyone who walks on Mars will likely only explore a tiny fraction of the planet's surface.

But there are no oceans or other bodies of water on Mars. Can an astronaut walk around Mars? How long would it take to walk around Mars?

It would take a long time—but exactly how long is hard to say. If the astronauts could keep walking at a constant speed, forever, this would be a simple calculation.

We basically need two parameters," said Eldar Yigit, an associate professor of physics and astronomy at George Mason University. Those parameters are the astronauts' speed (rate and direction) and the distance they will travel.

"If one walked along the equator of Mars, one would need to travel about 13,300 miles (21,400 km) to go around the planet. If one walked along the poles, one would travel about 100 miles (160 km) less, but the extreme cold would become a more challenging hurdle than the harsh conditions on other parts of the planet," Yigit said.

Yigit added: "A person's speed is about 3.1 miles per hour (5 kilometers per hour), which is the average walking speed on Earth, walking along the equator." Although the gravity on Mars is reduced compared to Earth (about 40% of Earth's), Yigit suspects that a person's walking speed on Mars would be very different. Like any backpack hiker on Earth, a walker on Mars would likely carry a lot of supplies, such as oxygen, water and food, and wear a bulky space suit.

If one were to travel around Mars at a constant speed, the calculations would be simple: just divide the distance traveled by the speed. This means that one orbit around Mars would take about 4,290 hours. A Martian day (called a "sol") is about 24.7 hours, so at a constant speed one orbit around Mars would take about 174 days. 174 days is a little more than a quarter of a Martian year, which is 668.6 Martian sols.

This oblique perspective view, generated from a digital terrain model, zenith and color channels from the high-resolution stereo camera on the space agency's Mars Express spacecraft, shows the landscape near the north pole of Mars. Extensive undulating dunes, towering cliffs and steep slopes of glaciers, and smoother layers of dust and ice in the distance are shown. (Image credit: ESA/DLR/FU Berlin)

Of course, no one could walk around Mars at a constant speed. Even if someone could carry enough oxygen, water, and food, and eat as they go, they would still need to stop to sleep. Assuming the astronauts slept eight hours a night, that would add up to about 56 sols. If someone stopped for four or five more hours a day to eat, rest, change clothes, and clean themselves, and to build or dismantle some type of bivouac, that would add up to another 30 or 35 sols, depending on how long they stayed.

Overall, a more realistic estimate is probably at least 265 Martian days, or about 40 percent of a Martian year. But this calculation doesn't take into account potential obstacles, such as rugged terrain. Mars has many mountains, including some taller than any on Earth, as well as valleys, craters, and many other geographical features that would make travel difficult.

Of course, it's unlikely that anyone would walk around Mars. While people have walked around Earth, it's impossible to completely circle the planet due to the presence of oceans. Despite multiple trips to the moon, humans have only walked on a small part of it. And walking so long and so far on Mars would bring many logistical problems, such as carrying enough food, water and oxygen, and protecting people from dangerous radiation.

Although it is unlikely that humans will be able to hike across the entirety of Mars, sending astronauts to the surface still has many advantages over using a rover, Yigit said.

“Rovers are susceptible to dust and other electrical problems; unexpected things can happen,” he said. With humans, “even if we have problems, we can find solutions.”

BY:Rebecca Sohn

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