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Mercury - The Hot Planet

NASAs Messenger mission will soon send back new images of Mercury. If you remember anything about Mercury, remember that it is the closest planet to the Sun and really hot. Temperatures on Mercury get up to 460 degrees Celsius. An average temperature on Earth is about 15 degrees Celsius (although it has a wide range). The Sun beats down on little Mercury all day long.

The amazing thing is that there is a side of Mercury that faces away from the Sun. Temperatures on the dark side of the planet can drop to less than negative 180 degrees Celsius. It's a whopping 640 degree temperature change from the hottest to the coldest part of the planet. The temperature ranges are a direct result of the very long days on Mercury. It takes 58 Earth days for Mercury to complete one of its days. This slow rotation affects the temperatures on the surface. Very long days allow the temperature to build for long periods of time.

As if the extreme temperatures weren't enough, Mercury has almost no atmosphere. The loss of atmosphere also allows for extreme temperature changes. Mercury, like the Moon, is covered with craters. Because the planet has no atmosphere, the asteroids never burn off. Imagine if you put our Moon next to the Sun. That comparison helps you understand what Mercury is really like. Tons of space dust and tiny asteroids are always hitting the Earth but our atmosphere helps to burn them up before they hit the planet. Asteroids have hit Mercury for millions of years. Each hit leaves its mark like the ones on our Moon.

Exploring Mercury

When Mariner 10 explored Mercury in the 1970's we received pictures and discovered that Mercury has a weak magnetic field, but similar to Earth's because it is a global magnetic field. Scientists think the core of the planet is made of nickel and iron. This iron acts like a huge magnet, changing the way fields interact with the planet. Something else is very interesting. It seems that Mercury lost a huge amount of its mantle/lithosphere millions of years ago. It may have hit another large object while orbiting the Sun. That fact means the layer of rock that covers the core is very thin when compared to other terrestrial planets. Astronomers hope to learn more about the geology and magnetic fields of Mercury when the MESSENGER probe reaches the planet in 2011. The recently launched probe will conduct scientific experiments for one year.

Touring Mercury

Mercury is very difficult to see from Earth. Why? It is right next to the Sun. Mercury is rarely in the sky in a position where we can see it because it is only visible during the day. Also, Mercury reflects less than 10% of the light that hits it. Scientists use the word albedo to describe how much light a surface will reflect. The low albedo of Mercury tells you that the surface is very dark. We have been able to see some parts of the planet, such as the Caloris Planitia Basin. The CP Basin is a very old crater caused by an asteroid impact millions of years ago. Scientists have also seen long cliffs called scarps. They may have been created when the planet was cooling.

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Messenger Orbits Mercury (NASA Video)
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Keywords for Review

Kinetic Energy: The energy of an object related to the motion of the object. On a simple level, an object that is not moving has no kinetic energy. An object that is moving has some amount of kinetic energy. The more an object moves, the more kinetic energy it has. An object increases its kinetic energy if it accelerates and increases its velocity. For example, as you increase the temperature of a gas, the molecules become more energetic and the system has an overall increase in kinetic energy. Kinetic Energy=(0.5)* mass * (velocity)2

Exothermic: A chemical reaction that releases energy after the reaction is complete. The energy is usually released as heat, but it can also be released as light or sound. On a small scale, a burning candle releases light and heat because of exothermic reactions as the wax burns. On a large scale, an explosion might occur when blasting with sticks of dynamite (TNT).

Activation Energy: The least amount of energy needed for a chemical reaction to occur. Reactions often require some amount of energy to get moving. For example, placing hydrogen and oxygen gases in a container will not give you water. There is a certain amount of energy required to get the first reaction going. Catalysts are substances that help to lower activation energies so that reactions can proceed.

Viscosity: A term used to measure the fluidity of a liquid. As the attractions between the molecules increase, viscosity increases. Fluids with high viscosities don’t flow easily. Some substances such as honey or sap are very slow moving and have high viscosities. Other fluids such as water or mercury (Hg) have very low viscosities.

Volatile: Volatility is the likelihood that a substance will vaporize (become a gas). Volatility measurements are all about comparing two substances. Substances with a higher vapor pressure are more volatile. Alcohol is more volatile than water because it evaporates at a lower temperature.

Reference Materials

Encyclopædia Britannica: http://www.britannica.com/EBchecked/topic/369668/matter
NYU.edu: http://www.nyu.edu/pages/mathmol/textbook/whatismatter.html
NASA: http://www.grc.nasa.gov/WWW/k-12/airplane/state.html
NASA: http://astroventure.arc.nasa.gov/teachers/pdf/AV-Astronolesson-Part2.pdf
Wikipedia: http://en.wikipedia.org/wiki/States_of_matter


 
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- Cosmos4Kids: Venus
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- Physics4Kids: Light

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