Posted on by Jerry Coffey

How Did Neptune Get Its Name?

Neptune Hurricanes
The "surface" of Neptune, its uppermost layer, is one of the most turbulent and active places in the Solar System. Credit: NASA/JPL

How did Neptune get its name? Shortly after its discovery, Neptune was only referred to as “the planet exterior to Uranus” or as “Le Verrier’s planet”. The first suggestion for a name came from Johann Galle, who proposed the name Janus. Another proposal was Oceanus. Urbain Le Verrier, who discovered the planet, claimed the right to name his discovery: Neptune. Soon Neptune became the internationally accepted name.

In roman mythology, Neptune was the god of the sea. The demand for a mythological name seemed to be in keeping with the nomenclature of the other planets, all of which, except for Earth, were named for Greek and Roman mythology. Most languages today use some variant of the name “Neptune” for the planet.

Now that you know how the planet was named, how about some facts about the planet itself. Size wise, the planet has an equatorial radius 24,764 km, a polar radius of 24,341 km, and a surface area of 7.6408×10,sup>9km2. It has a volume of 6.254×1013km3, a mass of 1.0243×1026kg, and a mean density of 1.638 g/cm3.

Its atmosphere is composed primarily of hydrogen and helium along with traces of hydrocarbons and nitrogen. It also contains a high proportion of ices like: water, ammonia, and methane. Astronomers occasionally categorize Neptune as an ice giant. The interior of Neptune is primarily composed of ices and rock. Traces of methane in the outermost regions account for the planet’s blue appearance. Neptune’s atmosphere is notable for its active and visible weather patterns. These weather patterns are driven by the strongest sustained winds of any planet in the Solar System, with recorded wind speeds as high as 2,100 km/h.Because of its great distance from the Sun, Neptune’s outer atmosphere is one of the coldest places in the Solar System, with temperatures at its cloud tops approaching ?218°C. Temperatures at the planet’s center are approximately 5,000°C. Neptune is one of the most interesting planets in our solar system. There are plenty of other articles about the planet here on Universe Today.

We have written many articles about Neptune for Universe Today. Here’s an article about the size of Neptune, and here’s an article about the atmosphere of Neptune.

If you’d like more information on Neptune, take a look at Hubblesite’s News Releases about Neptune, and here’s a link to NASA’s Solar System Exploration Guide to Neptune.

We’ve also recorded an entire episode of Astronomy Cast all about Neptune. Listen here, Episode 63: Neptune.

Source: NASA

Posted on by Jerry Coffey

Which Planet Has The Longest Day?

Mariner 10's Venus. Image: NASA
Mariner 10's Venus. Image: NASA

Just to be clear, this answer to ‘which planet has the longest day’ is based on this criteria: a planets day is how long it takes it to complete one rotation on its axis. This is also referred to as its rotational period. So, Venus has the longest day of any planet in our solar system. It completes one rotation every 243 Earth days. Its day lasts longer than its orbit. It orbits the Sun every 224.65 Earth days, so a day is nearly 20 Earth days longer than its year.

Length Of A Day On The Planets In Our Solar System

Mercury: 58 days and 15 hours
Venus: 243 days
Mars: 24 hours, 39 minutes and 35 seconds
Jupiter: 9.9 hours
Saturn: 10 hours 45 minutes 45 seconds, but can only be approximated because of atmospheric density.
Uranus: 17 hours, 14 minutes and 24 seconds
Neptune: 16 hours, 6 minutes and 36 seconds, but it is a bit more complicated than that. The equator and poles rotate at different speeds. You would have to do more research on the planet to fully understand the varying day on Neptune.

Now, back to why the Venusian day is longer than its year. Venus is closer to the Sun; therefore, its orbit takes a shorter period of time than its rotation upon its axis. The planet also rotates in retrograde. That means it spins in the opposite direction of the Earth. If you were standing on Venus, you could see the Sun rise in the West and set in the East.

A manned Venus flyby mission was proposed in the late 1960s. The mission was planned to launch in late October or early November 1973, and would have used a Saturn V rocket to send three men. The flight would have lasted approximately one year. The spacecraft would have passed approximately 5,000 km from the surface about four months into the flight. There have been several unmanned probes and flybys of the planet, including MESSENGER and the Venus Express. Future proposed missions include the BepiColombo, Venus InSitu Explorer, and the Venera-D.

We have written many articles about Venus for Universe Today. Here are some interesting facts about planet Venus, and here are some pictures of planet Venus.

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

We’ve also recorded an entire episode of Astronomy Cast all about Venus. Listen here, Episode 50: Venus.

Posted on by Jerry Coffey

What Is Mars Atmosphere Made Of

What is Mars Atmosphere Made Of
Planet Mars

[/caption]I think that one of the most interesting questions that have been posed of late is ‘what is Mar’s atmosphere made of?’ There has been a great deal of study done on this topic and interest is increasing since the discovery of methane, a possible indicator of life.

The atmosphere of Mars is over 95% carbon dioxide, 95.32% to be exact. The breakdown of gases goes like this:

  • Carbon dioxide 95.32%
  • Nitrogen 2.7%
  • Argon 1.6%
  • Oxygen 0.13%
  • Carbon monoxide 0.07%
  • Water vapor 0.03%
  • Nitric oxide .0013%
  • Trace gases(including krypton, methane, etc)

    • The Martian atmosphere has four main layers: lower, middle, upper, and exosphere. The lower atmosphere is a warm region(around 210 K). It is warmed by airborne dust(1.5 micrometers across) and heat radiated from the surface. This airborne dust gives the planet its ruddy brown appearance. The middle atmosphere is features a jetstream similar to Earth’s. The upper atmosphere is heated by the solar wind and the temperatures are much higher than at the surface. This heat separates the gases. The exosphere starts at about 200 km and has no clear end. It just tapers off into space.

    The carbon dioxide in the atmosphere freezes for part of the year and may drop to the surface. As much as 25% of the atmospheric carbon dioxide condenses at the polar caps into solid ice(dry ice) because the Martian poles are not exposed to sunlight during the planet’s winter. When the poles are again exposed to sunlight, the ice returns to its gas form and rises back into the atmosphere. So, a significant annual variation in the atmospheric pressure and atmospheric composition around the Martian poles.

    The methane mentioned earlier is used to show the possibility of life on Mars. While it is a byproduct of life, it is also a result of volcanism, geothermal process, and hydrothermal activity. Methane is an unstable gas, so there has to be a source on the planet that is constantly replenishing it. It has to be a very active source, because studies have shown that the methane is destroyed in less than on Earth year. It is thought that peroxides and perchlorates in the soil or that it condenses and evaporates seasonally from clathrates.

    Now you answer ‘ what is Mar’s atmosphere made of?’ the next time it comes up. You can be sure that the methane component will continue to be studied by rovers, orbiters, and, in the future, astronauts.

    We have written many articles about the atmosphere of Mars for Universe Today. Here’s an article about the air on Mars, and here’s an article about Mars’ comparison with Earth.

    If you’d like more info on Mars, check out Hubblesite’s News Releases about Mars, and here’s a link to the NASA Mars Exploration home page.

    We’ve also recorded an episode of Astronomy Cast all about Mars. Listen here, Episode 52: Mars.

    Reference:
    NASA Mars Fact Sheet

    Posted on by Jerry Coffey

    Why Does Saturn Have Rings

    Why Does Saturn Have Rings

    Saturn has fascinated amateurs and professionals alike for centuries. As quickly as the planet’s ring system was discovered the popular question became ‘why does Saturn have rings?’ usually followed by ‘what are Saturn’s rings made of?’. Well, here are the answers to both questions.

    The simplest answer as to why Saturn has rings and what they are made of is that the planet has accumulated a great deal of dust, particles, and ice at varying distances from its surface. These items are most likely trapped by gravity. The rings appear because of the wavelengths of light reflected by these rings of debris.

    Some scientists speculate that Saturn may be too big. Its gravitational pull is so strong that it has been able to snatch debris from space. Some of which is as large as an entire building. That pull is why it has at least 62 moons. Those moons contribute dust to the rings as well as absorb dust from the rings.

    A common theory as to how all of the material initially accumulated in Saturn’s rings is a series of asteroid impacts. Not with the planet, but with the moons around it. After the impact the remnants of the asteroids and the debris from the moons could not escape the gravitational pull of the planet.

    One other theory holds that the rings of Saturn formed as other moons broke apart in ancient times. Additionally, this theory states that some of the material could be from earlier, during the formation of the solar system, and Saturn could not accrete the material while it was forming and it has been in orbit ever since.

    No matter which theory you believe, the rings of Saturn are spectacular. After researching Saturn’s rings a little more, be sure to investigate the ring systems around Neptune, Uranus, and Jupiter. Each system is fainter than Saturn’s, but still interesting.

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

    If you’d like more info on Saturn, check out Hubblesite’s News Releases about Saturn. And here’s a link to the homepage of NASA’s Cassini spacecraft, which is orbiting Saturn.

    We’ve also recorded an episode of Astronomy Cast all about Saturn. Listen here, Episode 59: Saturn.

    Reference:
    NASA

    Posted on by Jerry Coffey

    What Causes Wind?

    Oxygen is a valuable biosignature because Earth is oxygen-rich, and because life made all that oxygen. But if we find oxygen in an exoplanet atmosphere does that mean life made it? Or is there an abiotic source of oxygen? Image Credit: NASA

    It was not until recent memory that what causes wind was understood. Wind is caused by air flowing from high pressure to low pressure. The Earth’s rotation prevents that flow from being direct, but deflects it side to side(right in the Northern Hemisphere and left in the Southern), so wind flows around the high and low pressure areas. This movement around is important for very large and long-lived pressure systems. For small, short-lived systems (outflow of a thunderstorm) the wind will flow directly from high pressure to low pressure.

    The closer the high and low pressure areas are together, the stronger the pressure gradient, so the winds are stronger. On weather maps, lines of constant pressure are drawn(isobars). These isobars are usually labeled with their pressure value in millibars (mb). The closer these lines are together, the stronger the wind. The curvature of the isobars is also important to the wind speed. Given the same pressure gradient (isobar spacing), if the isobars are curved anticyclonically (around the high pressure ) the wind will be stronger. If the isobars are curved cyclonically (around the low pressure) the wind will be weaker.

    Friction from the ground slows the wind down. During the day convective mixing minimizes this effect, but at night(when convective mixing has stopped) the surface wind can slow considerably, or even stop altogether.

    Wind is one way that the atmosphere moves excess heat around. Directly and indirectly, wind forms for the primary purpose of helping to transport excess heat in one of two ways: away from the surface of the Earth or from warm regions(tropics) to cooler regions. This is done by extratropical cyclones, monsoons, trade winds, and hurricanes. Now, you have the answer to what causes wind and its primary function on our planet.

    We have written many articles about the wind for Universe Today. Here’s an article about wind energy, and here’s an article about how wind power works.

    If you’d like more info on wind, check out Visible Earth Homepage. And here’s a link to NASA’s Earth Observatory.

    We’ve also recorded an episode of Astronomy Cast all about planet Earth. Listen here, Episode 51: Earth.

    Posted on by Jerry Coffey

    What did Isaac Newton Invent?

    Classical Mechanics
    Isaac Newton, Father of Classical Mechanics

    Sir Issac Newton is best know for his laws of motion. Many people’s knowledge of his scientific contributions stops there. Issac Newtons inventions contributed a great deal to our current understanding of subjects from optics to theology and how early scientists were able to view their world.

    In mathematics Isaac Newton inventions included laying the ground work for differential and integral calculus. His work was based on his insight that the integration of a function is merely the inverse procedure to differentiating it. Taking differentiation as the basic operation, he produced simple analytical methods that unified many separate techniques previously developed to solve apparently unrelated problems such as finding areas, tangents, the lengths of curves and the maxima and minima of functions.

    Issac Newton inventions in mechanics and gravitation were summarized the Principia. His discoveries in terrestrial and celestial mechanics showed how universal gravitation provided an explanation of falling bodies on Earth and of the motions of planets, comets, and other bodies in the heavens. He explained a wide range of then unrelated phenomena: the eccentric orbits of comets, the tides and their variations, the precession of the Earth’s axis, and motion of the Moon as perturbed by the gravity of the Sun. This work includes Newton’s three famous laws of motion, fluid motion, and an explanation of Kepler’s laws of planetary motion.

    Isaac Newton inventions in optics included his observation that white light could be separated by a prism into a spectrum of different colors, each characterized by a unique refractivity. He proposed the corpuscular theory of light. He was the first person to understand the rainbow. He was the first person to use a curved mirror in a telescope to prevent light form being broken up into unwanted colors.

    Isaac Newton inventions and contributions to science were many and varied. They covered revolutionary ideas and practical inventions. His works in physics, mathematics and astronomy are still important today. His contributions in any one of these fields would have made him famous; taken as a whole, they make him truly outstanding.

    We have written many articles about Isaac Newton’s inventions for Universe Today. Here’s an article about celestial mechanics, and here’s an article about Newton’s laws of motion.

    If you’d like more info on Isaac Newton’s inventions, check out How Stuff Works for an interesting article about Isaac Newton’s inventions, and here’s a link to Isaac Newton’s Biography.

    We’ve also recorded an entire episode of Astronomy Cast all about Gravity. Listen here, Episode 102: Gravity.

    Sources:
    How Stuff Works
    University of Virginia
    NASA

    Posted on by Jerry Coffey

    Largest River In The World

    Nile River
    Nile River

    [/caption]The largest river in the world can be hard to calculate. Many factors come into play: the source, the identification of the mouth, and the measurement of the river length between source and mouth. As a result, the measurements of many rivers are only approximations. So, there has been disagreement whether the Amazon or the Nile is the world’s largest river based on the inclusion of estuaries.

    The mouth of a river is hard to determine in cases where the river has a large estuary that gradually widens and opens into the ocean. The source of some rivers starting in farming areas can be difficult to determine, if the river is formed by the confluence of several farm field drainage ditches which only contain water after rain. Similarly, in rivers starting in a chalk area the length of the upper course which is dry varies with how high the water table is. How large a river is between source and mouth may be hard to determine due to issues of map scale. Small scale maps tend to generalize more than large scale maps. In general, length measurements should be based on maps that are large enough scale to show the width of the river, and the path measured is the path a small boat would take down the middle of the river.

    Given, and despite, this ambiguity, the Nile has been determined to be the largest river in the world followed by the Amazon and the Yangtze. The Nile is a north-flowing river in North Africa. It is 6,650 km long. It has two major tributaries, the White Nile and the Blue Nile. The Blue Nile is the source of most of the water and fertile soil in the system. The White Nile is longer and rises in central Africa beginning in Rwanda. The two rivers meet near the Sudanese capital of Khartoum. The northern section of the Nile flows almost entirely through desert. Most of the ancient civilizations of the area were centered along the river’s banks. The Nile ends in a large delta that empties into the Mediterranean Sea.

    The debate over which is the largest river in the world seems to be over for now. The Nile is 250 km larger than the Amazon. Both rivers have played important roles in the evolution of the civilizations that sprang up around them and will continue to do so for centuries to come.

    We have written many articles about rivers for Universe Today. Here’s an article about the world’s widest river, and here’s an article about the longest river in the world.

    If you’d like more info on rivers, check out Visible Earth Homepage. And here’s a link to NASA’s Earth Observatory.

    We’ve also recorded an episode of Astronomy Cast all about planet Earth. Listen here, Episode 51: Earth.

    Sources:
    http://news.nationalgeographic.com/news/2007/06/070619-amazon-river.html
    http://news.bbc.co.uk/2/hi/6759291.stm

    Posted on by Jerry Coffey

    Deepest Hole In The World

    Deepest Hole In The World
    Deepest Hole In The World. Image Source: chattablogs.com

    [/caption]

    The deepest hole in the world is on the Kola peninsula of Russia near the Norwegian border. This hole is being drilled for scientific study purposes and is currently over 12,200 meters deep.

    In 1926, Harold Jeffreys hypothesized that a transition zone within the crust, identifiable on seismic records as a “jump” in seismic velocity, could be attributed to a change in rock type from granite to a denser basalt. The deepest hole in the world being drilled at the Kola well has now penetrated about halfway through the crust of the Baltic continental shield, exposing rocks 2.7 billion years old at the bottom. One of the more fascinating scientific findings to emerge from this well is that the change in seismic velocities was not found at a boundary marking(Jeffreys’ hypothetical transition from granite to basalt), but it was at the bottom of a layer of metamorphic rock that extended from about 3.5 to about 9.8 km beneath the surface. This rock had been thoroughly fractured and was saturated with water. Free water should not be found at these depths. This could only mean that water which had originally been a part of the chemical composition of the rock minerals themselves had been forced out and prevented from rising by a cap of impermeable rock.

    This discovery has an impact on geophysical sciences and there is a potential economic impact. This water is very highly mineralized, and is a primary concentrating agent for most ore deposits. The technology for mining at these depths is not yet available. In order to get their single drill hole down as far as they did, the Soviets had to resort to experimental methods. Their chief innovation was that, instead of turning the drill bit by rotating the stem, in the Kola well the bit alone was turned by the flow of drilling mud.

    As drilling continues at the deepest hole in the world many scientists are hoping for additional discoveries and a greater understanding of the inner workings and makeup of our planet.

    We have written many articles about the deepest hole in the world for Universe Today. Here’s an article about how far the center of the Earth is, and here’s a forum discussion about the drillings through the Earth’s crust.

    If you’d like more info on the Earth’s deepest hole, check out the 10 amazing holes in the Earth. And here’s a link to NASA’s Earth Observatory.

    We’ve also recorded an episode of Astronomy Cast all about planet Earth. Listen here, Episode 51: Earth.

    Source: Wikipedia

    Posted on by Jerry Coffey

    What Causes Earthquakes?

    False-color composite image of the Port-au-Prince, Haiti region, taken Jan. 27, 2010 by NASA’s UAVSAR airborne radar. The city is denoted by the yellow arrow; the black arrow points to the fault responsible for the Jan. 12 earthquake. Image credit: NASA
    False-color composite image of the Port-au-Prince, Haiti region, taken Jan. 27, 2010 by NASA’s UAVSAR airborne radar. The city is denoted by the yellow arrow; the black arrow points to the fault responsible for the Jan. 12 earthquake. Image credit: NASA

    The two main answers to ‘how earthquakes happen’ is: as a result of tectonic plates colliding and volcanic eruption. The shock waves associated with nuclear weapons testing and other man-made explosions. To be considered an earthquake a shock wave has to be of natural origin.

    Earthquakes Caused By Tectonic Plates:
    The theory of plate tectonics explains how the crust of the Earth is made of several plates, large areas of crust which float on the Mantle. Since these plates are free to slowly move, they can either drift towards each other, away from each other or slide past each other. Many earthquakes happen in areas where plates collide or slide past each other. The Elastic Rebound Theory applies to these quakes.

    Major earthquakes are sometimes preceded by a period of changed activity. This might take the form of more frequent minor shocks as the rocks begin to move,called foreshocks, or a period of less frequent shocks as the two rock masses temporarily ‘stick’ and become locked together. Following the main shock, there may be further movements, called aftershocks, which occur as the rock masses settle into their new positions. Aftershocks cause problems for rescue services because they can bring down buildings that were weakened by the main quake.

    Earthquakes Caused By Volcanoes:
    Volcanic earthquakes are far less common than tectonic plate related ones. They are triggered by the explosive eruption of a volcano. When a volcano explodes the associated earthquake effects are usually confined to an area 16 to 32 km around its base.

    The volcanoes which are most likely to explode violently are those which produce acidic lava. Acidic lava cools and sets very quickly when it contacts air. This chokes the volcano’s vent and blocks the escape of pressure. The only way a blockage can be removed is by the pressure building up until it literally explodes the blockage outward.

    The volcano will explode in the direction of its weakest point, so it is not always upward. Extraordinary levels of pressure can produce an earthquake of considerable magnitude. The shock waves have been known to produce a series of tsunami in some instances.

    There you have the answer to ‘how earthquakes happen’. Keep in mind that there have been man-made shock waves following large explosions, but they are not considered earthquakes because of their artificial origin.

    We have written many articles about earthquakes for Universe Today. Here’s an article about the biggest earthquake, and here are some pictures of earthquakes.

    If you’d like more info on earthquakes, check out the U.S. Geological Survey Website. And here’s a link to NASA’s Earth Observatory.

    We’ve also recorded related episodes of Astronomy Cast about Plate Tectonics. Listen here, Episode 142: Plate Tectonics.

    Sources:
    http://earthquake.usgs.gov/learn/topics/plate_tectonics/rift_man.php
    http://www.geo.mtu.edu/UPSeis/where.html
    http://www.geo.mtu.edu/volcanoes/hazards/primer/eq.html
    http://news.discovery.com/earth/are-volcanoes-and-earthquakes-related.html

    Posted on by Jerry Coffey

    What are the Different Types Of Earthquakes?

    Earthquakes

    There are two main types of earthquakes: natural and man-made. Naturally occurring(tectonic) earthquakes occur along tectonic plate lines(fault lines) while man-made earthquakes are always related to explosions detonated by man.

    Tectonic earthquakes will occur anywhere there is sufficient stored elastic strain energy to drive fracture propagation along a fault plane. Plate boundaries move past each other smoothly and aseismically if there are no irregularities or asperities along the boundary that increase the frictional resistance; however, most boundaries do have such asperities that lead to stick-slip behavior. Once the boundary has locked, continued relative motion between the plates leads to increasing stress and stored strain energy around the fault surface. The energy increases until the stress breaks through the asperity, suddenly allowing sliding over the plate and releasing the stored energy. This energy is released as a combination of radiated elastic strain seismic waves, frictional heating, and cracking of the rock, which all adds up to an earthquake. This process is called the elastic rebound theory. It is estimated that only 10 percent or less of an earthquake’s total energy is radiated as seismic energy. Most of the earthquake’s energy is used to power the fracture growth or is converted into heat generated by friction.

    Occasionally, naturally occurring earthquakes happen away from fault lines. When plate boundaries occur in continental lithosphere, deformation is spread out over a much larger area than the plate boundary, so earthquakes occur away from the plate boundary and are related to strains developed within the broader zone of deformation caused by major irregularities in the fault trace. Also, all tectonic plates have internal stress fields caused by their interactions with neighboring plates and sedimentary loading or unloading. These stresses may be sufficient to cause failure along existing fault planes, giving rise to intraplate earthquakes.

    The other type of earthquake is the artificial or man-made quake. This type of quake has been felt all over the world after the detonation of a nuclear weapon. There is very little actual data that is readily available on this type of quake, but, of the two types of of earthquakes it is the only type that can be easily predicted and controlled.

    We have written many articles about earthquakes for Universe Today. Here’s an article about how earthquakes happen, and here’s an article about famous earthquakes.

    If you’d like more info on earthquakes, check out the U.S. Geological Survey Website. And here’s a link to NASA’s Earth Observatory.

    We’ve also recorded related episodes of Astronomy Cast about Plate Tectonics. Listen here, Episode 142: Plate Tectonics.

    Sources:
    Types of Earthquakes
    http://en.wikipedia.org/wiki/Earthquake
    http://earthquake.usgs.gov/learn/topics/plate_tectonics/rift_man.php