Category: Guide to Space

”Does Mars have seasons?” is an easy question to answer. Yes, Mars has seasons. The planet experiences all four seasons that the Earth does, but, since the year is longer on the planet, the axial tilt is different, and Mars has a more eccentric orbit than Earth, the seasons are not the same length as each other or the same in each hemisphere. Why does Mars have seasons? Because, like Earth, its axis is tilted away from the Sun.

On Mars, in the northern hemisphere to be exact, spring is the longest season. The Martian year is nearly twice as long as an Earth year(1.88 years), the seasons last longer as well. Here is how a Martian year in the north breaks down: Spring…7 months, Summer…6 months, Fall…5.3 months, and Winter…just over 4 months. Even in the summer months it is very cold. Temperatures at the height of the season may not top -20 C. In the south the temperatures can be as much as 30 C warmer during the same season. The great fluctuations in temperature and the difference in warmth between hemispheres can cause huge dust storms. Some can affect just a small area, while others can cover the entire planet. The larger storms usually occur when the planet is near its aphelion(closest point to the Sun). When there are global dust storms there is no way for scientists to visualize the planet’s surface.

Now that you have the answer to ”does Mars have seasons?”, you might wonder if the planet has always had the same climate. Most scientists doubt it has. Scientific evidence suggests that the planet has seen warmer and colder periods over its existence, much like Earth has. A radar instrument on the Mars Express has turned up water ice, a mineral mapping instrument has discovered chemicals formed in a wet environment, and its camera has picked out features on the surface formed by running water. The cameras also show a huge valley, Kasei Valles, that was probably carved by a gigantic glacier. Additional research has shown evidence of glaciers at varying latitudes. This would seem to indicate that the planet formerly had a different degree of axial tilt, which would have made for a much different environment and potential seasonal variations.

Mars does have seasons. They are not the same as the seasons the planet experienced millenia ago and may not be the same in the future. Earth has seen the same climate changes. Planetary evolution is ongoing, hopefully the spacecraft on and around the planet will tell us more, soon.

Here’s an article describing Spirit surviving 1000 days on Mars, going through all the seasons. And another on the discovery of mid-latitude glaciers on Mars, evidence that the planet was much more tilted in the past.

Here is some great information from the Adler Planetarium about the Martian climate and seasons. And some more detailed information from Malin Space Science Systems.

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:
NASA
Geosociety.org

How cold is Mars? Now, that is a fine question. The average temperature across the Martian surface is -63 C. Parts of Mars have been known to drop as low as -123 C. There are two main reasons that Mars is colder than Earth: it is farther from the Sun and it has an atmosphere that is too thin to retain heat.

The Martian atmosphere contains greenhouse gases that would cause a much warmer surface if the planet had the gravity and magnetic field that would allow it to hold onto gases. What little atmosphere(only 1% as thick as Earth’s) that clings to Mars is 95.32% carbon dioxide. As we know from experience here on Earth, higher amounts of CO₂ cause higher temperatures. We call it a greenhouse gas and blame global warming on the increase in these gases. If Mars could hold its carbon dioxide content, there would be runaway global warming across the planet.

The gravity on Mars is only 38% as strong as it is here on Earth. That low gravity allows many of the gases needed to retain heat close to the surface to escape into space. The core of the planet is thought to be solid. Without a spinning, molten core Mars is unable to generate a magnetic field. Without a magnetic field, the solar wind and radiation constantly bombard the Martian atmosphere, blowing away another portion of the gases needed to heat the planet.

There is evidence that Mars has not always been a frigid planet. Some probe instruments on the Mars Express suggest that at one time Mars was warm enough to support liquid water. A radar instrument has found water ice, a mineral mapping instrument discovered chemicals only formed in a wet environment, and a camera has shown features formed by running water. The Mars Advanced Radar for Subsurface and Ionospheric Sounding (MARSIS) has probed down to thousands of meters finding water ice along the way. The OMEGA Visible and Infrared Mineralogical Mapping Spectrometer has detected clay-like minerals that form during long-term exposure to water, sulphates(a mineral that forms when water evaporates), and ferric oxide. Each indicate the long term presence of liquid water on the surface. Images from the High Resolution Stereo Camera(HRSC) show features that could only be formed by erosion from flowing water.

The quick answer to ”how cold is Mars?” is -63 C on average. If you look into the contributing factors of that temperature, you must also look into the planet’s past. Some scientists think that Mars could have been a lush jungle like planet if it had not lost its atmosphere.

How cold is Mars? Read this article and learn that Mars is REALLY cold. And evidence that Mars has been cold for billions of years.

More information on Mars is available Hubblesite’s News Releases about Mars. Here’s an article from Space.com about how microbes can survive cold temperatures, maybe even some day on Mars.

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:
NASA Solar System Exploration Guide
NASA Mars Fact Sheet

The answer to “how far is Jupiter from Earth” can have a different answer every day of the year. The planets both travel in their elliptical orbits getting closer then farther apart. When Earth and Jupiter are at their closest to each other they are 628,743,036 km apart. At their most distant from each other they are 928,081,020 km apart. In astronomical units the distance varies from 4.2 AU to 6.2 AU.

All of the planets follow an elliptical orbit. When the planet is closest to the Sun it is called perihelion. When it is farthest it is called aphelion. The difference between perihelion and aphelion determines how eccentric an orbit is. Jupiter and Earth have two of the least eccentric orbits in our Solar System.

Earth and Jupiter are closest to each other when Earth is at aphelion and Jupiter is at perihelion. They are the most distant when they are on opposite sides of the Sun and both are at aphelion.

Jupiter is frequently the third brightest object in the night sky behind the Moon and Venus. When Earth and Jupiter are at their closest approach to each other, only the Moon can outshine the planet. Jupiter is so massive that it creates many effects throughout the Solar System. Some scientist believe that the tidal effects of Jupiter as it reaches perihelion could cause sunspots to increase in frequency. It is easy to understand how Jupiter could cause tidal effects when you consider that it is 318 times more massive than the Earth.

Despite its size, Jupiter rotates faster than any other planet in our Solar System. The speed of its rotation has flattened it more than some other planets. On Jupiter the poles are 4,600 km closer to the planet’s center than the equator is.

Jupiter’s mass and other aspects allow it to have a strong gravitational pull. That strong gravity has allowed the planet to capture many satellites. Currently, Jupiter is acknowledged to have 50 moons and 14 provisional moons. Many of those are thought to have been asteroids that were captured when they wandered too close to Jupiter’s influence.

The answer to ”how far is Jupiter from Earth” does not have a single clear cut answer. It varies day to day depending on the position of each planet in their respective orbits. There are many concrete answers about the planet to be had. All you have to do is a little research.

We have written many articles about Jupiter for Universe Today. Here are some interesting facts about Jupiter, and here’s an article about the color of Jupiter.

If you’d like more information on Jupiter, check out Hubblesite’s News Releases about Jupiter, and here’s a link to NASA’s Solar System Exploration Guide to Jupiter.

We’ve also recorded an episode of Astronomy Cast just about Jupiter. Listen here, Episode 56: Jupiter.

Sources:
http://www.nasa.gov/topics/solarsystem/features/jupiter_encounter.html
http://nssdc.gsfc.nasa.gov/planetary/factsheet/jupiterfact.html
http://www.bautforum.com/showthread.php/115427-Jupiter-drives-the-sunspots-and-here-s-how.?s=2ad4544667757a173842582ce0c49304
http://curious.astro.cornell.edu/question.php?number=564

The confirmed coldest temperature on Earth was recorded in Vostok, Antarctica at a brisk -89.2 degrees Celsius (183 Kelvin). There is an unconfirmed report of the temperature reaching -91 degrees Celsius (181 Kelvin); either way you look at it; you are still freezing your butt off.

The high velocity winds at the South Pole don’t make enduring the cold any easier by the dedicated scientists that work there. Winds can reach a velocity of 90 m/s. These temperatures were recorded during the Antarctic winter in June and July, during the period when the sun never actually rises. Even at its balmiest, Vostok only reaches temperatures of around -25 degrees Celsius (248 Kelvin). When we are looking at temperatures that cold, the Kelvin scale helps make the picture look less bleak; no ominous negative sign out front to make you lose all hope of getting warm. Incidentally, the warmest recorded temperature at Vostok was -19 degrees Celsius (254 Kelvin).

Vostok’s elevation is almost 3500 meters above sea level, and due to the density of oxygen being less towards the poles, the scientists are working at an effective height of 5000 meters above sea level.

Why would we journey to such an inviting place you might wonder? Vostok is located 1300 kilometers from the true South Pole, but is very near the Magnetic South Pole. Scientists study actinometry; the measure of solar radiation in photons, geophysics; the study of the physical properties of the Earth, mainly electrical, gravitational and magnetic forces which also includes seismology, and climatology; the study of weather systems.

Humanity may end in many different ways. We might kill ourselves through nuclear war, or die from a global disease epidemic. Like all the species on Earth, we’ll eventually be gone. But life will survive and continue to evolve into new and interesting forms. But even the Earth won’t last forever. Eventually, our planet too will end.

So, how will the Earth end? It all depends on how the Sun ends.

The Sun is a happy main sequence star right now, but as it nears the end of its life in about 7.5 billion years, it will begin to swell up as a red giant star. Its size will get so large that it will encompass the orbits of the inner planets. Mercury and Venus will be consumed within the Sun.

As the Sun grows, it will let off ferocious solar winds that dwarf its current winds. These winds will cause the Sun to lose a tremendous amount of mass, and this mass loss will cause the orbit of the planets to start spiraling outward. Scientists used to think that this spiraling outward might actually save Earth. Instead of being consumed by the Sun, it would keep spiraling, always keeping one step away from the expanding Sun.

The current thinking is that it’s not going to be fast enough. Although Earth’s orbit will be spiraling outward, it won’t be fast enough to keep pace with the expansion of the Sun as it becomes a red giant. At some point, roughly 7.5 billion years from now, Earth will end; it’ll be gobbled up just like Mercury and Venus before it.

By that time, let’s hope that future humans have relocated to the outer Solar System. By that time, the habitability zone around the Sun will have expanded to the point that water can be a liquid around Kuiper belt objects, like the dwarf planet Pluto. Can you imagine sitting on a beach on Pluto?

You can read more about the end of the Earth in this article. And you can read about the end of the entire Universe in this article.

If you’re talking about majestic ice rings, like we see around Saturn, Uranus or Jupiter, then no, Earth doesn’t have rings, and probably never did. If there was any ring of dust orbiting the planet, we’d see it.

It’s possible that there were rings orbiting Earth in the past. Some scientists think that Earth’s gravity could have broken up a comet or asteroid that got too close to the planet, but didn’t actually collide. This is similar to what happened to Comet Shoemaker/Levy 9 that eventually crashed into Jupiter. First the giant planet tore the comet up, and then the pieces crashed into the planet on a later orbit.

In the case of Earth, it might have held onto a few ice particles that would have then orbited the planet, and eventually crashed through our atmosphere and burned up. Even the smallest particles of ice or dust create spectacular meteors in the sky, so there was a ring right now, we’d see these impacts all the time.

Other scientists think that a giant asteroid impact with Earth, such as the one the killed the dinosaurs 65 million years ago, might have kicked up a huge ring of debris around the planet. This ring would cast a shadow down on the surface of the Earth, changing the planet’s climate, and could last for a few million years at most.

Finally, humans have put up an artificial ring in the past. The US Military launched 480 million copper needles into orbit around Earth in a project called Project West Ford. Scientists could bounce radio signals off the needles and communicate between two locations on Earth. This worked for a few months after launch, until the needles were too far dispersed to allow for communication. In theory, if needles were continuously launched, it would be a functioning communications system, but it’s not necessary with modern communications satellites.

So Earth probably did have temporary rings in the past after asteroid impacts or cometary flybys, but Earth doesn’t have rings today.

The Earth has a mass of 5.97×10²⁴ kg.

You can also check out these books about the planet Earth from Amazon.com for more detailed information.

If you could actually break up the planet into its various parts, you’d get 32% iron, 30% oxygen, 15% silicon, 14% magnesium, and then all the other elements, with sulfur, nickel, calcium and aluminum being the most common.

The density of Earth is 5.5 g/cm³. This is actually the densest planet in the Solar System; however, this is partly because of the size of Earth. The next most dense planet is Mercury, and it would actually be more dense than Earth if it wasn’t so small. Earth pulls at itself with so much gravity, that it compacts down tighter than Mercury.

How did scientists find out the mass of Earth? By studying how things fall towards it. Gravity is created from mass. The more mass an object has, the more gravity it will pull with. If you can calculate how an object is being accelerated by the gravity of an object, like Earth, you can determine its mass.

In fact, astronomers didn’t accurately know the mass of Mercury or Venus until they finally put spacecraft into orbit around them. They had rough estimates, but once there were orbiting spacecraft, they could make the final mass calculations. We know the mass of Pluto because we can calculate the orbit of its moon Charon.

Of all the Jovian related questions that we get here at Universe Today, what is Jupiter made of is one of the most common. Jupiter is mainly composed of hydrogen and helium just like a star. Answering that question seems to open a flood of other questions about the gas giant, so here are some facts about Jupiter that should answer quite a few of them.

Jupiter does not have enough mass to ignite fusion and become a star like our Sun. Without that mass, Jupiter is also too cold for fusion. If Jupiter were to become 80 times more massive it would be able to generate enough heat for fusion through gravitational compression. Given that there isn’t that much mass in our Solar System, outside of the Sun, it is impossible for Jupiter to become a star. Can you imagine how scorched and barren all of the planets would be if ours was a binary star system?

Spectral analysis of Jupiter has revealed that in addition to hydrogen and helium, the planet is made of water, methane and ammonia. Those elements are in trace amounts. The core of the planet is thought to contain some rock and metallic hydrogen. Scientists estimate that the core is heated to 36,000 K. The planet is not just a ball of gas that you would be able to drop straight through. In addition to the rocky/molten metallic hydrogen core, there is a layer of liquid hydrogen and helium and areas where the hydrogen is in a supercritical state, meaning that it does not have distinct gas and liquid phases.

Another frequent question about Jupiter is about the ”stripes” that can be seen. Those stripes are actually an effect of the fast rotation of the planet. To be more specific, they are due to the combination of the planet’s rotation and that its gases are more intensely heated at the equator than the poles. This is similar to why the Earth has trade winds near the equator and jet streams near the poles…rising air interacts with the coriolis effect of the rotation and causes sideways deflections. Jupiter rotates much faster and has a thicker atmosphere, so its coriolis effect is much stronger, thus the stripes. Try this link for a more in depth explanation of the striations(stripes).

Just asking what is Jupiter made of only brings up a whole other set of questions. Be sure to keep looking and you will find plenty to stump your friends and teachers with.

We have written many articles about Jupiter for Universe Today. Here’s an article about the color of Jupiter, and here’s an article about the missions to Jupiter.

If you’d like more information on Jupiter, check out Hubblesite’s News Releases about Jupiter, and here’s a link to NASA’s Solar System Exploration Guide to Jupiter.

We’ve also recorded an episode of Astronomy Cast just about Jupiter. Listen here, Episode 56: Jupiter.

Sources:

• NASA: Solar System Exploration – Jupiter
• NASA – What is Jupiter?

Jupiter has been known since very ancient times, so how did Jupiter get its name? While it had many names throughout history, the Roman empire had the greatest influence over a wide portion of modern society, so the names accorded to planets by the Romans still hold sway over astronomy. The Romans named the planet after their king of gods, Jupiter, who was also the god of the sky and of thunder. Why choose to name the planet Jupiter? It was the largest object in the sky; therefore the most powerful; therefore Jupiter.

In the Roman pantheon, Jupiter began as the sky god, concerned mainly with wine festivals and associated with the sacred oak of the Capitol. Eventually, he was attributed the spoils of war and became a god of war. It was believed that he caused the armies to stand strong and be victorious. He was the main witness in all oaths. Jupiter was the central god in the Capitoline Triad along with Juno and Minerva. He remained Rome’s chief official deity throughout the Republican and Imperial eras, until the pagan system was replaced by Christianity. Jupiter granted Rome supremacy because he was ”the fount of the auspices upon which the relationship of the city with the gods rested”. He personified the divine authority of Rome’s highest offices, internal organization, and external relations: his image in the Republican and Imperial Capitol bore regalia associated with Rome’s ancient kings and the highest consular and Imperial honors. Roman consuls swore their oath of office in Jupiter’s name. To thank him for his help, and to secure his continued support, they offered him a white, castrated ox with gilded horns.

It is common practice for a planet, moon, and many other celestial bodies to get their names from Greek or Roman mythology as well as derive their astronomical symbol from that particular personality. Some examples are Neptune the God of the Sea, Mars the God of War, Mercury the Messenger, Saturn the God of Time and father of Jupiter, Uranus the father of Saturn, Venus the Goddess of Love, and Earth, well, Earth is the only planet to buck the Greco-Roman tradition.

The answer to how did Jupiter get its name is very simple. If you delve into the planet much deeper, you will find that the planet itself is a mystery that scientists are still trying to unravel.

We have written many articles about Jupiter for Universe Today. Here’s an article about how long it takes to get to Jupiter, and here’s an article about the temperature of Jupiter.

If you’d like more information on Jupiter, check out Hubblesite’s News Releases about Jupiter, and here’s a link to NASA’s Solar System Exploration Guide to Jupiter.

We’ve also recorded an episode of Astronomy Cast just about Jupiter. Listen here, Episode 56: Jupiter.

Sources:
NASA Solar System Exploration Guide
NASA StarChild

When you choose a telescope, there are two main kinds you can pick from, reflectors and refractors. Both can be wonderful for viewing the night sky. They use basically different methods to boost light from dim objects in the sky. Here’s how they work, and how they’re different.

Refractor Telescopes
Here’s what’s inside a basic refractor telescope. The job of the objective lens, opposite the eyepiece end, is to gather the light coming from a distant object, such as a star, and bend it into a single point of focus. A second lens’ (the eyepiece) job is to enlarge that focused image for our retina; it acts as a magnifying glass. Think of the focused light coming in from the first lens as a bug, and think of the eyepiece magnifier as a basic magnifying glass that we look at the bug with. That’s it in a nutshell.

Reflector Telescopes
A reflector telescope uses two mirrors instead of two lenses. Isaac Newton developed this telescope to combat chromatic aberration (a rainbow seen around some objects viewed with a refractor telescope). A mirror used to gather light doesn’t suffer from this effect. Light from an object enters the telescope tube and is reflected off a curved mirror at the end of the tube. A second, small, flat mirror in the middle of the tube reflects this image to the eyepiece. There are potential problems associated with the mirrors. Firstly, some light is always lost in the reflection; good quality telescopes can usually gather 90% of the light coming in. Secondly, the mirror might not be a perfect curve, so the image being reflected will not come to a perfect point. This results in a dragging effect; a point could be seen as a line or cross. Also, the mirrors need to be cleaned and realigned from time to time.