From this distance, it takes sunlight 13 minutes to travel from the Sun to Mars. As Mars orbits the Sun, it completes one rotation every Martian days are called sols — short for "solar day. Mars' axis of rotation is tilted 25 degrees with respect to the plane of its orbit around the Sun. This is another similarity with Earth, which has an axial tilt of Like Earth, Mars has distinct seasons, but they last longer than seasons here on Earth since Mars takes longer to orbit the Sun because it's farther away.
And while here on Earth the seasons are evenly spread over the year, lasting 3 months or one quarter of a year , on Mars the seasons vary in length because of Mars' elliptical, egg-shaped orbit around the Sun. Spring in the northern hemisphere autumn in the southern is the longest season at sols. Autumn in the northern hemisphere spring in the southern is the shortest at days.
Mars has two small moons, Phobos and Deimos , that may be captured asteroids. They're potato-shaped because they have too little mass for gravity to make them spherical. Phobos, the innermost and larger moon, is heavily cratered, with deep grooves on its surface. It is slowly moving towards Mars and will crash into the planet or break apart in about 50 million years.
Deimos is about half as big as Phobos and orbits two and a half times farther away from Mars. Oddly-shaped Deimos is covered in loose dirt that often fills the craters on its surface, making it appear smoother than pockmarked Phobos. Mars has no rings. However, in 50 million years when Phobos crashes into Mars or breaks apart, it could create a dusty ring around the Red Planet.
When the solar system settled into its current layout about 4. Mars is about half the size of Earth, and like its fellow terrestrial planets, it has a central core, a rocky mantle, and a solid crust. Mars has a dense core at its center between and 1, miles 1, to 2, kilometers in radius. It's made of iron, nickel, and sulfur. Surrounding the core is a rocky mantle between and 1, miles 1, to 1, kilometers thick, and above that, a crust made of iron, magnesium, aluminum, calcium, and potassium.
This crust is between 6 and 30 miles 10 to 50 kilometers deep. The Red Planet is actually many colors. At the surface, we see colors such as brown, gold, and tan. This dust gets kicked up into the atmosphere and from a distance makes the planet appear mostly red.
Its volcanoes, impact craters, crustal movement, and atmospheric conditions such as dust storms have altered the landscape of Mars over many years, creating some of the solar system's most interesting topographical features. A large canyon system called Valles Marineris is long enough to stretch from California to New York — more than 3, miles 4, kilometers.
What happened? At some point in the distant past, the red planet gained its two small and irregularly shaped moons, Phobos and Deimos. The two lumpy worlds, discovered in , are named for the sons and chariot drivers of the god Mars in Roman mythology. How the moons formed remains unsolved. But recent models instead suggest that they could have formed from the debris flung up from Mars after a huge impact long ago.
Deimos, the smaller of the two moons, orbits Mars every 30 hours and is less than 10 miles across. Its larger sibling Phobos bears many scars, including craters and deep grooves running across its surface. Scientists have long debated what caused the grooves on Phobos. Since the s, humans have robotically explored Mars more than any other planet beyond Earth. Currently, eight missions from the U.
But getting safely to the red planet is no small feat. Of the 45 Mars missions launched since , 26 have had some component fail to leave Earth, fall silent en route, miss orbit around Mars, burn up in the atmosphere, crash on the surface, or die prematurely.
More missions are on the horizon, including some designed to help search for Martian life. NASA is building its Mars rover to cache promising samples of Martian rock that a future mission would return to Earth. In , the European Space Agency and Roscosmos plan to launch a rover named for chemist Rosalind Franklin , whose work was crucial to deciphering the structure of DNA.
The rover will drill into Martian soil to hunt for signs of past and present life. Other countries are joining the fray, making space exploration more global in the process. In July , the United Arab Emirates is slated to launch its Hope orbiter , which will study the Martian atmosphere.
Perhaps humans will one day join robots on the red planet. NASA has stated its goal to send humans back to the moon as a stepping-stone to Mars. Will humans eventually build a scientific base on the Martian surface, like those that dot Antarctica? How will human activity affect the red planet or our searches for life there? Time will tell. But no matter what, Mars will continue to occupy the human imagination, a glimmering red beacon in our skies and stories.
All rights reserved. Mars Nearing Earth In , the Hubble Space Telescope snapped this photo of the red planet 11 hours before its closest approach to Earth in 60, years.
Longer year and shifting seasons With a radius of 2, miles, Mars is the seventh largest planet in our solar system and about half the diameter of Earth. Share Tweet Email. Why it's so hard to treat pain in infants. This wild African cat has adapted to life in a big city. The solar wind is powerful, but molecules like carbon dioxide have a high molecular weight, meaning it's difficult to get them up to escape velocity.
Could the loss of a magnetic field coupled with the solar wind provide a viable mechanism to transform Mars from an atmosphere-rich world with liquid water at its surface to the Mars we know today? Without the protection of an active magnetic field, the solar wind constantly strikes Mars's If we were to infuse Mars, today, with an Earth-like atmosphere, the solar wind would whittle it back down to its present density in a mere few tens of millions of years.
During flaring events, where the solar wind becomes much stronger than normal, that increases to about twenty times the typical value. When the atmosphere was much denser, though, the same level of solar wind would strip it away much more quickly. After perhaps a billion years with liquid water precipitating and flowing freely on the Martian surface, a tiny slice of cosmic history was enough to blow the habitable prospects of Mars completely away.
Both Mars and Earth had early atmospheres that were heavy, massive, and extraordinarily rich in CO 2. While Earth's carbon dioxide got absorbed into the oceans and locked up into carbonate rocks, Mars was unable to do the same, as its oceans were too acidified.
The presence of sulfur dioxide led to Martian oceans that were rich in sulfuric acid. This led to geology of Mars we've discovered with rovers and landers, and pointed to a different cause — the solar wind — as the culprit in the mystery of the missing Martian atmosphere.
Some four billion years ago, the core of Mars became inactive, its magnetic field disappeared, and the solar wind stripped the atmosphere away. With our magnetic field intact, our planet will remain blue and alive for the foreseeable future. But for a smaller world like Mars, its time ran out long ago. At last, we finally know why. This is a BETA experience. You may opt-out by clicking here. More From Forbes. Nov 12, , am EST. Nov 11, , pm EST. Nov 11, , am EST.
Nov 10, , pm EST. Nov 9, , pm EST. Nov 9, , am EST. Edit Story. May 14, , am EDT. Ethan Siegel Senior Contributor. James St. James Van Gundy. Lundin et al.
Follow me on Twitter. Check out my website or some of my other work here. Ethan Siegel.
0コメント