Why does mars have moons

A major collision is the only explanation that fits on all counts. Given that so many pieces of evidence needed to be combined to reveal the origin of our own moon, it makes sense to gather any and all potentially relevant information about Mars and its moons. Sure, our simulations pretty definitively show that no combination of collisional parameters would have produced two small moons around Mars and nothing else, but that does not rule out an impact scenario for the origin of Phobos and Deimos.

Observational sciences, like astronomy, are fundamentally different from laboratory sciences where you can perform and control your experiments however you like. In an observational science, all you get is a snapshot of what the system you are examining is like over the very brief interval you get to observe it.

For our solar system, which has been around for over 4. The moons of Mars were only discovered in the late 19th century, less than years ago. To claim that Mars has two moons is certainly correct, today, but we have to keep the cardinal rule of all observational sciences in mind whenever we draw conclusions. When we look at what we have, today, all we are seeing are the survivors.

It is eminently possible that what exists today is just a subset of what once existed long ago. When we look at Mars, it is easy to notice its surface features, which are numerous and varied and tell a dramatic story.

Mars has a reddish color to it, evidence of widespread ferric oxide: the result of reactions taking place between iron and oxygen. The atmosphere of Mars is rich in both water vapor and carbon dioxide, both of which can oxidize iron and also combine to point toward a wet, watery history on the red planet. Its presently thin, tenuous atmosphere with what appear to be dried-up riverbeds on its surface and hematite spheres in lowland regions further indicate a watery past, with a much thicker atmosphere that must have persisted for a billion years or more.

But another spectacular feature of Mars is its heavily cratered outer layer, with dramatic highlands and lowlands. Although there are a number of prominent features like mountains, volcanoes, basins, and multiple layers of craters, perhaps the most dramatic difference can be seen between the northern and southern hemispheres of the red planet. While there are topographical variations across both hemispheres, there is an enormous basin covering half of the planet, where for some reason, roughly 50 percent of Mars is around five kilometers three miles lower in elevation than the rest of the planet.

How could this be possible? Even on a geologically active world like Earth, such a configuration probably never existed. Even back when the continents were all interconnected, forming Pangaea, there were likely large ridges, subduction zones, and other tremendous variations in elevation along the ocean floor, preventing the uniform, deep basin that has persisted on Mars for at least the past 3 billion years or so. It is generally quite difficult to make a planet lopsided like this, particularly if its structure is driven by gradual, internal processes.

However, there is an easy way to make a large, deep, sustaining basin: from a large impact. Not, mind you, the type of impact that created our own moon, which required a Mars-sized body striking a world nearly as large as Earth already is today.

Instead, a slower collision between perhaps a Pallas -sized body Pallas being the 3rd largest asteroid in our asteroid belt, well behind Ceres but nearly as massive as Vesta and early Mars could have left a dramatic scar of precisely this type. I am not attempting to suggest that a slow, massive collision kicked up debris that then created Phobos and Deimos; that is not consistent with any realistic scenario.

And people may one day do just that. Scientists have discussed the possibility of using one of the Martian moons as a base from which astronauts could observe the Red Planet and launch robots to its surface, while shielded by miles of rock from cosmic rays and solar radiation for nearly two-thirds of every orbit.

Like Earth's Moon, Phobos and Deimos always present the same face to their planet. Both are lumpy, heavily-cratered and covered in dust and loose rocks.

They are among the darker objects in the solar system. The moons appear to be made of carbon-rich rock mixed with ice and may be captured asteroids. A pound 68 kilogram person would weigh two ounces 68 grams there. Yet NASA's Mars Global Surveyor has shown evidence of landslides, and of boulders and dust that fell back down to the surface after being blasted off the moon by meteorites. Hall named the moons for the mythological sons of Ares, the Greek counterpart of the Roman god, Mars.

Phobos means fear and Deimos means dread. Fitting names for the sons of a war god. The fast-flying moon appears to travel from west to east. Deimos orbits much farther away, tending to stay 12, miles 20, km from the red planet's surface.

The moon takes about 30 hours, a little over a Martian day, to travel around its host. Because of their odd shapes and strange composition, scientists thought for a long time that both moons were born asteroids. Jupiter's gravity could have nudged them into orbit around Mars, allowing the red planet to capture them. But the orbits of the moons make such a birth appear unlikely. Both moons take stable, nearly circular paths around the red planet.

Captured bodies tend to move more erratically. An atmosphere could have slowed the pair down and settled them into their present-day orbits, but the air on the Martian planet is thin and insufficient for such a task. It is possible that the moons formed like the planet, from debris left over from the creation of Mars. Gravity could have drawn the remaining rocks into the two oddly shaped bodies. Or, the moons could have spawned from a violent birth, much like Earth's moon.

A collision, common in the early solar system, could have blown chunks of the red planet into space, and gravity may have pulled them together into the moons. Similarly, an early moon of Mars could have been impacted by a large object, leaving Phobos and Deimos as the only remaining bits.

Mars ' tidal rates aren't strong enough to alter their orbits in such a way that put them into their current formation. Instead, these orbits suggest they formed "in situ" around Mars, in particular in an extended disc of debris, likely from a giant collision. This impact could even be responsible for the spin rate of Mars.

This impact likely produced many other now-extinct moons , too, but it is unclear why Mars ended up with two small moons from such an impact and not a single large satellite like ours.

To come to this conclusion, Pascal Rosenblatt and colleagues from the Royal Observatory of Belgium simulated a giant impact event on Mars.