Gravity on Mars

by Jerry Coffey on June 5, 2008

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NASA's Hubble Space Telescope took this close-up of the red planet Mars

What is the gravity on Mars? NASA's Hubble Space Telescope took this close-up of the red planet Mars


The gravity on Mars is much lower than it is here on Earth, 62% lower to be more precise. That means that Martian gravity is 38% of Earth’s. A person weighing 100 kg here would tip the scales at 38 kg there.

I know that kg is a measure of mass, not weight, but if you live in a metric system and you step on a bathroom scale, it’s going to measure in kilograms.

Mars is smaller than Earth in all the factors that determine the gravity of a planet. Mass, density, and size are a few of them. Newton used the universal law of gravitation to describe how gravity works; however, this only described the phenomenon in part. Einstein hypothesized that space and time served as the fabric of the universe. He stated that gravity was simply a curvature in space-time created by a mass object. The curvature in space created by an object with greater mass than the objects around it would cause these objects of lesser mass to fall toward the more massive object, but this only described gravity on the large scale. Then came quantum physics. Quantum physics introduced particles smaller than neutrons, electrons, and protons, which displayed exceptions to classical physics of matter when viewed on the micro scale. Quantum physics proposed a theoretical particle called the graviton that controls gravity, so now we have our current understanding of gravity, yet the phenomenon is still a partial mystery that is an obstacle to a universal theory to describe the functions of every interaction in the universe accurately.

The affects of long term exposure to different strengths of gravity is an area of study concerning human exploration of other planets. It is known that humans can suffer bone loss and other health problems, but exact studies need to be conducted to test the top-end duration of a human mission. MIT researchers have proposed one such study involving a group of mice. The mice would be launched aboard a small satellite, which would be spun so that the force mimics Mars’ gravity. In the proposition 15 mice will orbit Earth for five weeks. The mission is called the Mars Gravity Biosatellite Program. The project could cost over $15 million plus the cost of the launch and is still seeking funding. By 2009, the project had engaged over 600 undergraduate, graduate, and high school students in aerospace engineering, space life sciences, and program management, earning multiple student awards. The mission is currently scheduled to launch in 2014 or 2016.

Overcoming the reduced gravity (Mars) could be a major stepping off point for long term human exploration of other planets. Scientists have very little data to go on, so, hopefully, the Mars Gravity Biosatellite will launch soon and expand that knowledge.

Here’s an article on Universe Today about how the reduced Martian gravity will be tested on mice in space. And another about how the lower gravity on Mars helps it make huge sand dunes.

Information on the Mars Gravity Biosatellite. And the kids might like this; a project they can build to demonstrate Mars gravity.

Finally, if you’d like to learn more about Mars in general, we have done several podcast episodes about the Red Planet at Astronomy Cast. Episode 52: Mars, and Episode 91: The Search for Water on Mars.

Sources:
http://solarsystem.nasa.gov/planets/profile.cfm?Object=Mars&Display=Facts
http://web.mit.edu/newsoffice/2004/mars-biosatellite.html

susan October 8, 2008 at 11:23 AM

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Physics teacher January 12, 2009 at 10:06 AM

In paragraph one, “kg” should be replaced by “lbs” or “Newtons.” Kilograms is a unit of mass – not weight. Mass does not change because gravity is different.

Also, the smaller radius of Mars would tend to make the gravity greater. Its the mass of the moon that makes its gravity less.

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