How Long Is A Year On The Other Planets? - Universe Today Universe Today How Long Is A Year On The Other Planets? Article Updated: 29 Jan , 2016 by Matt Williams Here on Earth, we to end to not give our measurements of time much thought. Unless we’re griping about Time Zones, enjoying the extra day of a Leap Year, or contemplating the rationality of Daylight Savings Time, we tend to take it all for granted. But when you consider the fact that increments like a year are entirely relative, dependent on a specific space and place, you begin to see how time really works. Here on Earth, we consider a year to be 365 days. Unless of course it’s a Leap Year, which takes place every four years (in which it is 366). But the actual definition of a year is the time it takes our planet to complete a single orbit around the Sun. So if you were to put yourself in another frame of reference – say, another planet – a year would work out to something else. Let’s see just how long a year is on the other planets, shall we?

A Year On Mercury: To put it simply, Mercury has an orbital period of 88 days (87.969 to be exact), which means a single year is 88 Earth days – or the equivalent of about 0.241 Earth years. But here’s the thing. Because of Mercury’s slow rotation (once every 58.646 days) and its rapid orbital speed (47.362 km/s), one day on Mercury actually works out to 175.96 Earth days. MESSENGER maps of Mercury – a monochrome map at 250 m/pixel and an eight-color (left), 1-km/pixel color map. Small gaps will be filled in during the next solar day (right). Credit: NASA/Johns Hopkins University APL/Carnegie Institution of Washington So basically, a single year on Mercury is half as long as a Mercurian (aka. Hermian) day. This is due to Mercury being the closest planet to the Sun, ranging from 46,001,200 km at perihelion to 69,816,900 km at aphelion.

At that distance, the planet shoots around the Sun faster than any other in our Solar System and has the shortest year. In the course of a year, Mercury experiences intense variations in surface temperature – ranging from 80 °K (-193.15 °C;-315.67 °F) to 700 °K (426.85 °C; 800.33 °F). However, this is due to the planet’s varying distance from the Sun and its spin, which subjects one side to extended periods of extremely hot temperatures and one side to extended periods of night. Mercury’s low axial tilt (0.034°) and its rapid orbital period means that there really is no seasonal variation on Mercury. Basically, one part of the year is as hellishly hot, or horribly cold, as any other. A Year On Venus: The second closest planet to our Sun, Venus completes a single orbit once ever 224.7 days. This means that a single year on Venus works out to about 0.6152 Earth years. But, once again, things are complicated by the fact that Venus has an unusual rotation period.

In fact, Venus takes 243 Earth days to rotate once on its axis – the slowest rotation of any planet – and its rotation is retrograde to its orbital path. The planet Venus, as imagined by the Magellan 10 mission. Credit: NASA/JPL Combined with its orbital period, this means that a single solar day on Venus (the time between one sunup to the next) is 117 Earth days. So basically, a single year on Venus is lasts 1.92 Venusian (aka. Cytherean) days. Again, this would make for some confusing time-cycles for any humans trying to make a go of it on Venus! Also, Venus has a very small axial tilt – 3° compared to Earth’s 23.5° – and its proximity to the Sun makes for a much shorter seasonal cycle – 55-58 days compared to Earth’s 90-93 days. Add to that its unusual day-night cycle, variations are very slight. In fact, the temperate on Venus is almost always a brutal 736 K (463 °C ; 865 degrees °F), which is hot enough to melt lead!

A Year On Earth: Comparatively speaking, a year on Earth is pretty predictable, which is probably one of the reasons why life is able to thrive here. In short, our planet takes 365.2564 solar days to complete a single orbit of the Sun, which is why we add an extra day to the calendar every four years (i.e. a Leap Year, which 2016 happens to be). But because our axis is tilted, there is considerable variation in the seasons during the course of a year. During the winter, when one hemisphere is pointed away from the Sun, the Sun’s distance from the equator changes by up to 23.5°. As a result, between the summer and winter, the length of days and nights, temperatures, and seasons will go through significant changes. Above the Arctic Circle, an extreme case is reached where there is no daylight at all for part of the year – up to six months at the North Pole itself, in what is known as a “polar night”. In the southern hemisphere the situation is exactly reversed, with the South Pole experiencing a midnight sun, a day of 24 hours, again reversing with the South Pole.

Every six months, the order of this is reversed. A Year On Mars: Mars has one of the highest eccentricities of any planet in the Solar System, ranging from 206,700,000 km at perihelion and 249,200,000 km at aphelion. This large variation and its greater distance from the Sun, leads to a rather long year. Basically, Mars takes the equivalent of 687 (Earth) days to complete a single orbit around the Sun, which works out to to 1.8809 Earth years, or 1 year, 320 days, and 18.2 hours. On the other hand, Mars has a rotation period that is very similar to Earth’s – 24 hours, 39 minutes, and 35.244 seconds. So while the days on Mars are only slightly longer, the seasons are generally twice as long. But this is mitigated by the fact that seasonal changes are far greater on Mars, owing to its eccentricity and greater axial tilt (25.19°).

During the winter, the global atmospheric pressure on Mars is 25% lower than during summer. This is due to temperature variations and the complex exchange of carbon dioxide between the Martian dry-ice polar caps and its CO2 atmosphere. As a result, Martian seasons vary greatly in duration than those on Earth, change roughly every six months, and do not start on the same Earth day every Martian year. Mars 2001 Global Dust Storm, as captured by the Hubble Space Telescope. Credit: NASA/J. Bell (Cornell)/M. Wolff (SSI)/Hubble Heritage Team (STScI/AURA) A Year On Jupiter: Jupiter is another interesting case. Whereas the gas giant only takes 9 hours 55 minutes and 30 seconds to rotate once on its axis, it also takes alson 11.8618 Earth years to complete an orbit around the Sun. This means that a year on Jupiter is not only the equivalent of 4,332.59 Earth days, but 10,475.8 Jovian days. That’s a lot of sunrises!

Much like Venus, Jupiter has an axial tilt of only 3 degrees, so there is literally no seasonal variation between the hemispheres. In addition, temperature variations are due to chemical compositions and depths rather than seasonal cycles. So while it does have “seasons”, which change very slowly due to its distance from the Sun – each season lasts 3 years – they are not similar to what terrestrial planets experience. A Year On Saturn: Much like its fellow gas giant Jupiter, Saturn takes it time completing a single orbit of the Sun, but rotates on its axis very rapidly. All told, a year on the planet lasts the equivalent of 10,759 Earth days (or about 29 1?2 years). But since it only takes 10 hours, and 33 minutes to complete a single rotation on its axis, a year on Saturn works out to 24,491.07 Saturnian (aka. Cronian) days. This portrait looking down on Saturn and its rings was created from images obtained by NASA’s Cassini spacecraft on Oct. 10, 2013. Credit: NASA/JPL-Caltech/Space Science Institute/G.

Ugarkovic Due to its axial tilt of almost 27 degrees (slightly more than Mars), Saturn experiences some rather long seasonal changes. But due to it being a gas giant, this does not result in variations in temperature. Combined with its distance from the Sun (at an average distance of 1,429.39 million km or 9.5 AU), a single season lasts more than seven years. A Year On Uranus: Uranus has some of the strangest annual and seasonal variations of any planet in the Solar System. For one, the gas/ice giant takes about 84 Earth years (or 30,688.5 Earth days) to rotate once around the Sun. But since the planet takes 17 hours, 14 minutes and 24 seconds to complete a single rotation on its axis, a year on Uranus lasts 42,718 Uranian days. However, this is confounded due to Uranus’ axial tilt, which is inclined at 97.77° towards the Sun. This results in seasonal changes that are quite extreme, and unique to Uranus. In short, when one hemisphere is pointed towards the Sun (i.e.

in summer), it will experience 42 years of continuous light. In winter, the situation is reversed, with this same hemisphere experiencing 42 years of continuous darkness. A Year On Neptune: Given its distance from the Sun, Neptune has the longest orbital period of any planet in the Solar System. As such, a year on Neptune is the longest of any planet, lasting the equivalent of 164.8 years (or 60,182 Earth days). But since Neptune also takes comparatively little time to rotate once on its axis (16 hours, 6 minutes and 36 seconds), a single year lasts a staggering 89,666 Neptunian days. Reconstruction of Voyager 2 images showing the Great Black spot (top left), Scooter (middle), and the Small Black Spot (lower right). Credit: NASA/JPL What’s more, with an axial tilt close to Earth and Mars’ (28.5 degrees), there is some seasonal variation on the planet. Essentially, a single season lasts more than 40 years. But like all gas/ice giants, this does not result in noticeable temperature variations.

Orbit And Rotation Orbit And Rotation ORBIT AND ROTATION ON PLANET MARS Mars' average distance from the Sun is roughly 230 million km (1.5 AU) and its orbital period is 687 (Earth) days. The solar day (or sol) on Mars is only slightly longer than an Earth day: 24 hours, 39 minutes, and 35.244 seconds. A Martian year is equal to 1.8809 Earth years, or 1 year, 320 days, and 18.2 hours. Mars's axial tilt is 25.19 degrees, which is similar to the axial tilt of the Earth. As a result, Mars has seasons like the Earth, though on Mars they are about twice as long given its longer year. Mars passed its perihelion in June 2007 and its aphelion in May 2008. Mars has a relatively pronounced orbital eccentricity of about 0.09; of the seven other planets in the Solar System, only Mercury shows greater eccentricity.

However, it is known that in the past Mars has had a much more circular orbit than it does currently. At one point 1.35 million Earth years ago, Mars had an eccentricity of roughly 0.002, much less than that of Earth today. The Mars cycle of eccentricity is 96,000 Earth years compared to the Earth's cycle of 100,000 years. However, Mars also has a much longer cycle of eccentricity with a period of 2.2 million Earth years, and this overshadows the 96,000 year cycle in the eccentricity graphs. For the last 35,000 years Mars' orbit has been getting slightly more eccentric because of the gravitational effects of the other planets. The closest distance between the Earth and Mars will continue to mildly decrease for the next 25,000 years. Orbit & Rotation of Mars: Planet Mars’ Year, Day, Spin & Revolution – PlanetFacts.org The Moon Orbit and Rotation of Mars Mars distance from the Sun is 230 million km and its orbital period is equal to 687 Earth days.

For this planet, the solar day is only a bit longer than that of the Earth’s day which is 24 hours, 39 minutes and 35.244 seconds. An entire Martian year would equal 1.8809 in Earth years. Mars’ axial tilt is 25.19 degrees, which is quite similar to that of our own planet and in this way, seasons in Mars are very much like the seasons that we have here on Earth. However, on Mars, they are almost twice as long because of the fact that the planet has significantly longer years compared to us. At the moment, the orientation of Mars’ North Pole is close to Deneb. The planet has passed its perihelion in April 2009 and its aphelion in May 2007. It would reach its next perihelion in May 2011. Mars has a rather pronounced orbital eccentricity, which is about 0.09, compared to the other planets in the Solar System. The only other planet that shows greater eccentricity would be Mercury.

For the last 35,000 years, Mars’ orbit has grown even more eccentric due to the gravitation effects that the other planets have on it. In fact, the closest distance between our planet and Mars would continuously decrease for the next 25,000 years. As for its moons, Mars has two tiny natural ones. Phobos and Deimos orbit quite close to the planets. Currently, from what scientists know of their composition, it is believed that both moons were captured asteroids but this has never been completely ascertained nor confirmed. More about the Planet Mars Okello – Ajasi I can fly to Mars. Shishcobob Gives mee all the details mobie How Long is a Year on Mars? - Universe Today Universe Today How Long is a Year on Mars? Article Updated: 28 May , 2016 by Matt Williams Mars and Earth have quite a few things in common. Both are terrestrial planets , both are located within the Sun’s habitable zone , both have polar ice caps , similarly tilted axes , and similar variations in temperature .

And according to some of the latest scientific data obtained by rovers and atmospheric probes, it is now known that Mars once had a dense atmosphere and was covered with warm, flowing water . But when it comes to things like the length of a year, and the length of seasons, Mars and Earth are quite different. Compared to Earth, a year on Mars lasts almost twice as long – 686.98 Earth days. This is due to the fact that Mars is significantly farther from the Sun and its orbital period (the time it takes to orbit the Sun) is significantly greater than that of Earth’s. Orbital Period: Mars average distance (semi-major axis) from the Sun is 227,939,200 km (141,634,852.46 mi) which is roughly one and half times the distance between the Earth and the Sun (1.52 AU). Compared to Earth, its orbit is also rather eccentric (0.0934 vs.

0.0167), ranging from 206.7 million km (128,437,425.435 mi; 1.3814 AU) at perihelion to 249.2 million km (154,845,701 mi; 1.666 AU) at aphelion. At this distance, and with an orbital speed of 24.077 km/s, Mars takes 686.971 Earth days, the equivalent of 1.88 Earth years, to complete a orbit around the Sun. The eccentricity in Mars’ orbit means that it is . Credit: NASA This eccentricity is one of the most pronounced in the Solar System, with only Mercury having a greater one (0.205). However, this wasn’t always the case. Roughly 1.35 million years ago, Mars had an eccentricity of just 0.002, making its orbit nearly circular.

It reached a minimum eccentricity of 0.079 some 19,000 years ago, and will peak at about 0.105 in about 24,000 years from now. But for the last 35,000 years, the orbit of Mars has been getting slightly more eccentric because of the gravitational effects of the other planets. The closest distance between Earth and Mars will continue to mildly decrease for the next 25,000 years. And in about 1,000,000 years from now, its eccentricity will once again be close to what it is now – with an estimated eccentricity of 0.01. Earth Days vs. Martian “Sols”: Whereas a year on Mars is significantly longer than a year on Earth, the difference between an day on Earth and a Martian day (aka. “Sol”) is not significant. For starters, Mars takes 24 hours 37 minutes and 22 seconds to complete a single rotation on its axis (aka. a sidereal day), where Earth takes just slightly less (23 hours, 56 minutes and 4.1 seconds).

On the other hand, it takes 24 hours, 39 minutes, and 35 seconds for the Sun to appear in the same spot in the sky above Mars (aka. a solar day), compared to the 24 hour solar day we experience here on Earth. This means that, based on the length of a Martian day, a Martian year works out to 668.5991 Sols. The Opportunity rover captured this analemma showing the Sun’s movements over one Martian year. Images taken every third sol (Martian day) between July, 16, 2006 and June 2, 2008. Credit: NASA/JPL/Cornell/ASU/TAMU Seasonal Variations: Mars also has a seasonal cycle that is similar to that of Earth’s. This is due in part to the fact that Mars also has a tilted axis, which is inclined 25.19° to its orbital plane (compared to Earth’s axial tilt of approx. 23.44°).

It’s also due to Mars orbital eccentricity, which means it will periodically receive less in the way of the Sun’s radiance during at one time of the year than another. This change in distance causes significant variations in temperature. While the planet’s average temperature is -46 °C (51 °F), this ranges from a low of -143 °C (-225.4 °F) during the winter at the poles to a high of 35 °C (95 °F) during summer and midday at the equator. This works out to a variation in average surface temperature that is quite similar to Earth’s – a difference of 178 °C (320.4 °F) versus 145.9 °C (262.5 °F). This high in temperatures is also what allows for liquid water to still flow (albeit intermittently) on the surface of Mars. In addition, Mars’ eccentricity means that it travels more slowly in its orbit when it is further from the Sun, and more quickly when it is closer (as stated in Kepler’s Three Laws of Planetary Motion ).

Mars’ aphelion coincides with Spring in its northern hemisphere, which makes it the longest season on the planet – lasting roughly 7 Earth months. Summer is second longest, lasting six months, while Fall and Winter last 5.3 and just over 4 months, respectively. Artist’s impression of the seasons on Mars. Credit: britannica.com In the south, the length of the seasons is only slightly different. Mars is near perihelion when it is summer in the southern hemisphere and winter in the north, and near aphelion when it is winter in the southern hemisphere and summer in the north. As a result, the seasons in the southern hemisphere are more extreme and the seasons in the northern are milder. The summer temperatures in the south can be up to 30 K (30 °C; 54 °F) warmer than the equivalent summer temperatures in the north. Weather Patterns: These seasonal variations allow Mars to experience some extremes in weather. Most notably, Mars has the largest dust storms in the Solar System. These can vary from a storm over a small area to gigantic storms (thousands of km in diameter) that cover the entire planet and obscure the surface from view.

They tend to occur when Mars is closest to the Sun, and have been shown to increase the global temperature. The first mission to notice this was the Mariner 9 orbiter, which was the first spacecraft to orbit Mars in 1971, it sent pictures back to Earth of a world consumed in haze. The entire planet was covered by a dust storm so massive that only Olympus Mons, the giant Martian volcano that measures 24 km high, could be seen above the clouds. This storm lasted for a full month, and delayed Mariner 9‘s attempts to photograph the planet in detail. And then on June 9th, 2001 , the Hubble Space Telescope spotted a dust storm in the Hellas Basin on Mars. By July, the storm had died down, but then grew again to become the largest storm in 25 years. So big was the storm that amateur astronomers using small telescopes were able to see it from Earth. And the cloud raised the temperature of the frigid Martian atmosphere by a stunning 30° Celsius. These storms tend to occur when Mars is closest to the Sun, and are the result of temperatures rising and triggering changes in the air and soil.

As the soil dries, it becomes more easily picked up by air currents, which are caused by pressure changes due to increased heat. The dust storms cause temperatures to rise even further, leading to Mars’ experiencing its own greenhouse effect. Given the differences in seasons and day length, one is left to wonder if a standard Martian calendar could ever be developed. In truth, it could, but it would be a bit of a challenge. For one, a Martian calendar would have to account for Mars’ peculiar astronomical cycles, and our own non-astronomical cycles like the 7-day week work with them. Another consideration in designing a calendar is accounting for the fractional number of days in a year. Earth’s year is 365.24219 days long, and so calendar years contain either 365 or 366 days accordingly. Such a formula would need to be developed to account for the 668.5921-sol Martian year. All of this will certainly become an issue as human beings become more and more committed to exploring (and perhaps colonizing) the Red Planet. We have written many interesting articles about Mars here at Universe Today. and How Long is a Year on Other Planets?

, How Long is a Day on Mars? , How Long Does it Take Mars to Orbit the Sun? , Mars Compared to Earth , and Does Mars Have Seasons? For more information, check out NASA’s Solar System Exploration page on Mars . Astronomy Cast also has several interesting episodes on the subject. Like Episode 52: Mars , and Episode 91: The Search for Water on Mars . Share this: Curiosity 1 Martian Year Anniversary: NASA’s Rover Celebrates 687 Earth Days On The Red Planet Curiosity 1 Martian Year Anniversary: NASA’s Rover Celebrates 687 Earth Days On The Red Planet 06/24/14 AT 12:20 PM Close NASA’s Mars Curiosity Rover has just completed another milestone. Arriving on Mars in August 2012, Curiosity has already spent close to two years on the Red Planet, but Tuesday marks the one Martian year anniversary for the rover. NASA reports on the Martian anniversary for the Rover.

During its first Martian year on the Red Planet, Curiosity has already completed its primary scientific mission, fired more than 100,000 laser shots, drilled into two types of Martian rocks, is in the middle of a 5-mile trek to its next destination and, of course, took a selfie to celebrate the anniversary. The Curiosity rover landed in Gale Crater on Aug. 6, 2012 and its primary mission was to determine if the location could have once supported life. Curiosity found its answer in a pair of mudstone rocks in Yellowknife Bay in March 2013. Drilling into the mudstones, Curiosity found evidence Mars could have supported life and Gale Crater was once an ancient lakebed. NASA's Curiosity Mars Rover has spent one Martian year on the Red Planet. Photo: NASA/JPL-Caltech/MSSS According to NASA, other significant discoveries from Curiosity include: measuring the loss of Mars early atmosphere as well as determining the lack of methane , a biologically-produced gas, in the planet's atmosphere; and the age of a rock and how long it was exposed to radiation, which could determine when water last flowed on the planet.

Most recently, Curiosity drilled into a sandstone rock named " Windjana " which yielded more magnetite, a type of mineral. @EmreIsik_ Can and have! I take selfies from time to time to show the team the state of my hardware. pic.twitter.com/IIa2lD3dLs — Curiosity Rover (@MarsCuriosity) May 6, 2014 David Blake, principal investigator for Curiosity's Chemistry and Mineralogy (CheMin) instrument from NASA’s Ames Research Center, said in a statement, "A key question is whether this magnetite is a component of the original basalt or resulted from later processes, such as would happen in water-soaked basaltic sediments. The answer is important to our understanding of habitability and the nature of the early-Mars environment." The Windjana analysis revealed plenty of clay minerals as well as the mineral orthoclase, commonly found in the Earth's crust, notes NASA. "Windjana is still within an area where a river flowed. We see signs of a complex history of interaction between water and rock," said John Grotzinger, Curiosity Project Scientist from the California Institute of Technology.

— Curiosity Rover (@MarsCuriosity) April 16, 2014 Curiosity's onboard cameras have also captured some incredible moments including Mercury 's passage in front of the sun, a Martian solar eclipse and an asteroid . Unrelated to Curiosity's scientific mission, who could forget " Mars Rat " or the " Jelly doughnut rock ." To date, Curiosity has traveled 4.9 miles and has 2.4 miles before it reaches Mount Sharp, NASA reports. A video celebrating Curiosity's Martian year anniversary can be viewed below. Curiosity Team Celebrates 2nd Martian Year On Red Planet With Weather Report | Video Curiosity Team Celebrates 2nd Martian Year On Red Planet With Weather Report | Video By Steve Spaleta | May 11, 2016 05:38pm ET A Martian year is 668.6 sols (687 Earth days) and May 11th, 2016 is the Mars Science Laboratory's 1,337th sol on Mars. Curiosity project scientist Ashwin Vasavada highlights the data that the rover has compiled on all the Martian seasons.

Get Immersed in Curiosity's 360 Degree Mars Dune What are the periods of revolution and rotation of Mars? | Reference.com What are the periods of revolution and rotation of Mars? A: Quick Answer The period of revolution of Mars is 686.98 Earth days, and the period of rotation of Mars is 1.03 Earth days. A planet's period of revolution is the length of one year, or how long it takes the planet to revolve around the sun. A planet's period of rotation is the length of one day; that is, how long the planet takes to rotate once. Exploring the Planets | National Air and Space Museum Number of observed satellites: 2 Comparisons with Earth Average distance from Sun: 1.52 x Earth Diameter: 0.532 x Earth Density: 0.7 x Earth World of Change Mars has always intrigued us, but only in recent decades have we come to know our smaller neighbor as a world of great complexity. Telescopic views suggested to early observers that its climate changed seasonally. But we now know that even greater changes have occurred over billions of years. Great volcanoes have risen. Floodwaters have raced across the surface.

Giant impacts have altered the landscape. Today, wind is the only major force of change, but the rocks and soil and landscape still hold clues to the planet's past. Why has Mars changed so much over time? Did life evolve there when conditions were more favorable? Mars continues to challenge each new generation of explorers, and understanding Mars may help us discover our own future in the solar system. Earth and Mars Teeming with complex life and covered by vast oceans, Earth is unique among the planets of our solar system. Yet it shares common features and processes with Mars. Both planets have polar ice caps, their axes of rotation tilt at similar angles, and their days are almost the same length. The surfaces of both planets have been shaped by water, wind, and volcanism. The Planets Close You should all know that the Solar System consists of 9 planets, which all orbit around the Sun! Below, I have listed the planets in order from the Sun, and have got some information about each of them. Mercury Mercury is a very hot planet, mostly because it is the closest planet to the Sun orbiting at around 60 million kms away from the Sun.

The temperatures on Mercury can reach up to 430�C in the daytime. (800�F) That is over four times as hot as boiling water! But at night, it is very different, the temperature can sometimes drop to -180�C! (-300�F) Mercury is a very rocky, cratered planet as well. Mercury is a small planet in relation to some of the others in our Solar System, it is the second smallest planet in the Solar System, only 4,800km (3000 miles) in diameter. Mercury takes 88 days to do a complete orbit around the Sun, so a year on Mercury is only 88 Earth days. Mercury's days are very long though because it has a very slow rotation. 1 Mercury day is equal to 59 Earth days, which means there are less than two days in Mercury's year! Venus Even though Venus orbits the Sun at a distance of around 110 million kms, about 50 million kms further away than Mercury, Venus actually hotter than Mercury! Why?

Because Venus has a very thick atmosphere and cloud cover over itself, and most of the heat gets reflected away from the planet. But what heat does end up getting through Venus' thick clouds, gets trapped in there and can't get out, so it gets very hot in there! On the surface of Venus, temperatures can reach up to about 480�C! (around 900�F) This is what makes it the hottest planet in the Solar System. Mercury has no atmosphere or cloud cover etc to keep any heat in, so even though it is the closest planet to the Sun, it still isn't the hottest planet! Venus is also a very rocky planet, a bit like a desert. Venus takes longer to rotate, than it does to orbit the Sun. So a day on Venus, is actually longer than the year! Venus also rotates in the opposite direction to the other planets! Venus is 12,100km in diameter. Earth Well, you should know enough about this planet, you live on it! Earth takes 365 days to orbit the Sun, and it takes 24 hours to complete a rotation. Now I bet you never knew any of that!

Earth is only a little bit bigger than Venus, 12,700km in diameter, and orbits the Sun from a distance of around 150 million km. (around 93 million miles) Mars Mars orbits the Sun at a distance of about 225 million km (140 million miles). Mars take nearly 687 days to orbit the Sun. So 2 years on Earth, is roughly only 1 year on Mars. Mars is also only about half the size of planet Earth, about 6,500 km in diameter. Mars' surface has lots of rocks scattered all over it, and it is also very red. But why? Because Mars' surface has lots of iron in it, which has rusted away over millions of years, and rusty iron is obviously red! Scientists also think that Mars could support life on it. They hope to have people on Mars by the year 2015. A rover called Sojourner has already been on Mars. It was a little 6 wheeled buggy, powered by solar panels, and was remote-controlled from here on Earth by scientists. It has been on the surface of Mars since 1997.

Scientists have lost contact with the rover now though. Mars also has the largest volcano in the Solar System on it's surface, Olympus Mons. It rises 24km above the surface, and is 550 km across. The biggest volcano on Earth, Mauna Loa, in Hawaii is only 9 km high, and 120 km across. Although this volcano is big for here on Earth, it is pretty small in comparison with Olympus Mons! Mars also has some big canyons on it's surface. Some of them are as wide, as the Grand Canyon is long! Jupiter Jupiter, the king of the planets, orbits the Sun at a distance of 778 million km (483 million miles), and is 142,800 km in diameter, making it the biggest planet in our Solar System. Thats so big that more than 1000 planets the size of Earth could fit inside it! Jupiter is the first of the Gas Giant planets.

(Gas Giants are four of the outer planets, Jupiter, Saturn, Uranus and Neptune that are made up mostly of gas.) This means that you couldn't really land on Jupiter, you would just fall straight through it, because there is no solid land to land on! Jupiter has a very strong gravitational pull, and small objects (i.e. asteroids, meteoroids etc) that go too near it, get sucked into it. Jupiter also has a big storm raging across it's surface. This storm is commonly known as The Great Red Spot, because it looks just like a red spot on Jupiter's surface! The Great Red Spot is about 8 km (5 miles) high, around 40,000 km (25,000 miles) long, and about 14,000 km (8,700 miles) wide, and it's winds blow at about 500 km per hour (310 miles per hour). As it moves across the surface of Jupiter, it swallows up other smaller storms. But even though it does this, it is still shrinking. Now, it is only about half of the size it was 100 hundred years ago.

Jupiter also has a ring around it, like Saturn. It is very small though, in comparison to Saturn's, which you can easily see from Earth. These rings cannot be seen from Earth, they were discovered by one of the Voyager probes. >Saturn Saturn is the second largest planet in the Solar System, about 119,300 km (74,100 miles) across. Saturn orbits the Sun at a distance of around 1,425 million km (890 million miles)! Saturn rotates very quickly, taking just 10 hours to complete a rotation. Because of this, some of the gases that Saturn is made up of are flung towards it's equator. This make Saturn "bulge", making it fatter in the middle of the planet. Saturn is also a Gas Giant, like Jupiter. The planet itself is made up mostly of hydrogen. The atmosphere of Saturn is made up of lots of helium though, so Saturn is a very light planet in relation to the others. It is so light in fact, that if there was ever an ocean big enough that Saturn could fit in, it would float. Saturn also has a big ring system.

Saturn's rings are much bigger than Jupiter's though, and they are easily visible from Earth through a telescope. They are made up from lots of rocks, ranging in size from about 1 foot across to some the size of a car. Uranus Now we're getting a bit further out into the Solar System! Uranus is the third gas giant in the Solar System and is about 2,900 million km (1,800 million miles) away from the Sun. It is 50,800 km in diameter, and takes just over 84 years to do a complete orbit around the Sun. The atmosphere is made up mostly of hydrogen. It does have some helium and small amounts of other gases in it as well. Uranus has a strange spin, it rotates on it's side. This could have been caused by a collision with another large, planet-sized object millions of years ago, which tipped it over. Uranus spins a bit slower than Earth, it takes 18 hours to do a complete rotation. (And of course Earth takes 24 hours!) Uranus moves through space at about 7 km (4 � miles) per second.

In comparison, Earth moves at nearly 30 km (19 miles) a second. Uranus also has a ring system, but not as big and easily visible as Saturn's. They were discovered from Earth in 1977, then the Voyager probe gathered more information on them in 1986. The rings are made up mostly from dust. Neptune Neptune is the fourth and last Gas Giant in the Solar System. Neptune is over 4,500 million km (more than 2,800 million miles) away from the Sun, and takes nearly 165 years to do a complete orbit around the Sun. Neptune takes 16 hours to do a complete rotation, so a day on Neptune is 8 hours shorter than here on Earth. Astronomers thought that Neptune would be pretty plain, and dull looking because they hadn't seen much of it, mostly because it was to hard to see much of, because of its distance from Earth. The space probe Voyager 2 proved them wrong though - Neptune is just like the other Gas Giant planets. Neptune has storms raging across it's surface, ones similar to the Great Red spot on Jupiter.

Astronomers have seen a few dark spots on Neptune. The largest spot on Neptune, called the Great Dark Spot, is about the same size as the Earth. It is probably a huge storm like the Great Red Spot. This Great Dark Spot was seen by the Voyager 2 probe in 1989, but when astronomers searched for it using the Hubble Space Telescope in the 1990s, they could not find it! No one is certain as to why the spot disappeared, and no one can say if it will re-appear. Neptune is blue in colour because of the methane gas in it's atmosphere, which obviously is blue! In Neptunes atmosphere, there is also some hydrogen, helium, and water. Big clouds race around Neptune as well. They are pushed around by the fastest winds that have been found on any planet in the Solar System. Near the Great Dark Spot, winds blew at speeds of up to 2000 km per hour (1,200 miles per hour)! One of the clouds on Neptune goes around the planet every 16 hours! Astronomers have nicknamed this cloud Scooter, because of the speed it goes around Neptune at.

Pluto Now we've got to the last planet of the Solar System: Pluto. Pluto is very far away from the Sun. It's distance from the Sun changes a lot though, due to the difference in it's orbit . At it's closest to the Sun, Pluto is 4,425 million km, and at its furthest, it is 7,375 million km away! At times Pluto is the 8th planet from the Sun, and other times it is the 9th planet from the Sun. (See this image for an illustration of why this happens) Because of Pluto's great distance from the Sun, it takes a very long time to orbit the Sun. (The further a planet is away from the Sun, the slower it orbits the Sun) Pluto takes 249 years to orbit the Sun! Pluto takes 6 days to complete a rotation. Pluto's diameter is only around 2,300 km (1,429 miles, which makes it the smallest planet in the Solar System. Pluto is also a very cold planet, because of its distance from the Sun. This is the only planet that a space probe hasn't visited yet.

Scientists are working on sending one to Pluto sometime though, called the Pluto/Kupier Express, but even if it does go, it will be quite a while before it gets launched. I have heard that they have put the idea off all together, so they might not even send one there at all! Some astronomers think that Pluto may not even be a planet, because it is so far away from the Sun, and because it is so small. Click here to learn about other things in the Solar System, like comets and asteroids.

Question: Which planet has 687 Earth days to one year?
Answer: Mars