Author: Fraser Cain

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The interior of Mercury is remarkably similar to the interior of our own planet Earth. Like Earth, Mercury has a crust, mantle and core. But there are many differences between our two planets as well.

But when you look at Mercury, it appears very similar to our own Moon. It has the same rugged terrain and numerous impact craters. But Mercury has a very different interior from the Moon. When NASA’s Mariner 10 spacecraft made its flyby of Mercury in 1974, it helped astronomers calculate that Mercury is the second densest planet in the Solar System after Earth. In fact, if Mercury were the size of Earth and had our mass and gravity, it would be even more dense.

At the heart of Mercury is it’s core. This is a ball of liquid iron and other metals that measures approximately 3,600 km across. Considering the fact that Mercury itself is only 4,879.4 km across, the planet’s core accounts for 42% of its volume. Compare this to the Earth’s core, which only accounts for 17% of our planet’s volume.

Astronomers only learned recently that Mercury’s core is liquid, and not solid as originally theorized. They did this by studying how radio signals bounce off the surface of Mercury. They found that wobbles in the planet’s rotation matched predictions only if Mercury’s core was liquid.

Surrounding the core of Mercury is the mantle. Similar to Earth, this mantle consists of silicates, but it only measures 500-700 km thick. Compared this to the Earth’s mantle, which accounts for most of the volume of the planet.

And surrounding Mercury’s mantle is its crust. A region of the planet the measures between 100-300 km thick. Unlike the Earth’s crust, Mercury’s crust has no plate tectonics, so it doesn’t have plates that float above the interior of Mercury. Without these plate tectonics, even impact craters billions of years old are preserved on the planet’s surface.

We have written many stories about Mercury here on Universe Today. Here’s an article about a the discovery that Mercury’s core is liquid. And how Mercury is actually less like the Moon than previously believed.

If you’d like more information on Mercury, check out NASA’s Solar System Exploration Guide, and here’s a link to NASA’s MESSENGER Misson Page.

We’ve also recorded an entire episode of Astronomy Cast all about Mercury. Listen here, Episode 49: Mercury.

Interior de Mercurio

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Just how old is Mercury? Is it the oldest planet, or the youngest? Actually, you might be surprised to know that there is no oldest or youngest planet. Mercury is exactly the same age as all the rest of the planets in the Solar System: approximately 4.6 billion years old.

Astronomers think that our entire Solar System started out as a giant cloud of cold molecular hydrogen gas, left over from the Big Bang 13.7 billion years ago. Some event, like a nearby supernova explosion disturbed the cloud and caused it to begin collapsing. As it collapsed, various pieces broke off, each of which would eventually form a star like our own Sun.

Because of conservation of momentum from all the particles of hydrogen, the cloud began to spin as it collapsed, becoming a flattened disk. The newly forming Sun was at the center of this disk, with dust surrounding it. These dust particles collided together, forming larger and larger chunks of dust, rocks, boulders, asteroids, planetesimals, and eventually the planets we see today. All of the planets formed together at the same time.

How do we know how old Mercury is? Astronomers have found meteorites on Earth, that fell from space at some point in the past. They use a technique called radiocarbon dating to determine how old the meteorites are. No matter where the meteorites come from; the Moon, Mars, or the asteroid belt, they’re always the same age: 4.6 billion years.

And so, how old is Mercury? The same as everything in the Solar System: 4.6 billion years old.

We have written many stories about Mercury here on Universe Today. Here’s an article about a the discovery that Mercury’s core is liquid. And how Mercury is actually less like the Moon than previously believed. How old is the Universe?

If you’d like more information on Mercury, check out NASA’s Solar System Exploration Guide, and here’s a link to NASA’s MESSENGER Misson Page.

We have also recorded a whole episode of Astronomy Cast that’s just about planet Mercury. Listen to it here, Episode 49: Mercury.

Cuántos años tiene Mercurio

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Have you ever wondered how long it might take to travel to Mercury? At its closest point, Mercury gets to within 77.3 million km away from the Earth. Let’s see how long it takes for various spacecraft to get to Mercury.

For starters, let’s look at how long light itself takes to make the journey. Light takes only 4.3 minutes to travel from the Earth to Mercury when they’re at their closest point.

The fastest spacecraft ever launched from Earth is NASA’s New Horizons mission, currently on its way to visit Pluto and the outer Solar System. New Horizons is traveling at about 80,000 kilometers per hour. It would take about 40 days to get from the Earth to Mercury when they’re closest.

Of course, spacecraft don’t travel a straight route between planets, they follow a path that uses the least amount of energy, and so it takes them longer… a lot longer. The first spacecraft to actually make the journey to Mercury was NASA’s Mariner 10, which launched on November 3, 1973. It made its first Mercury flyby on March 29, 1974. Mariner 10 took 147 days to get from Earth to Mercury.

More recently, NASA’s MESSENGER spacecraft launched on August 3, 2004 to study Mercury in orbit. It made its first flyby on January 14th, 2008. That’s a total of 1,260 days to get from Earth to Mercury. So why did MESSENGER take so long? Engineers want the spacecraft to go into orbit around Mercury, and so it needs to be traveling at a slow enough velocity to be able to get into orbit without just flying past. It will finally enter orbit around Mercury in March, 2011.

We have written many stories about Mercury here on Universe Today. Here’s an article about a side of Mercury never before seen by spacecraft, and how Mercury is actually less like the Moon than previously believed.

If you’d like more information on Mercury, check out NASA’s Solar System Exploration Guide, and here’s a link to NASA’s MESSENGER Misson Page.

We have also recorded a whole episode of Astronomy Cast that’s just about planet Mercury. Listen to it here, Episode 49: Mercury.

Cuánto tiempo toma llegar a Mercurio

References:
NASA: Mariner 10
NASA Messenger Mission Page

Physics is such a comprehensive topic that no one could possible hope to include every aspect of it in one place. Entire libraries are dedicated to trying to do just that and they find something new to add every year. What Universe Today has done is compile a list of links to a wide variety of the physics topics that can be found on this site. To sort of intrigue you before you dive into the links, here are a few physics facts:

Absolute zero is -273.15º C. No lab has ever been able to produce it. Close, but no cigar.

Scientist know that nuclear fusion could produce enough energy to sustain our world throughout the remainder of its existence, but no one has ever been able to produce controlled nuclear fusion. The key to fusions success is in control.

John Dalton is known for creating the basis for the current atomic model, but did you know the first atomic model predates his by over 1,000 years?

According to the second law of thermodynamics, our universe will end in a horrible heat death.

Did you know that there is a large number of people who think that the Large Hadron Collider will actually create a black hole that will engulf the Earth from the surface? A little too much science fiction, don’t you think?

These are just a few of the interesting facts that you can find in the links below. Enjoy your hunting!

• Mass Driver
• What Did Isaac Newton Discover?
• What is Physics?
• Cherenkov Radiation
• 4th Dimension
• Alpha Radiation
• Convex Mirror
• How Do Microwaves Work?
• Blackbody Radiation
• Absolute Temperature
• 10 Dimensions
• Beta Radiation
• Boltzmann Constant
• Schrodinger’s Cat
• Hooke’s Law
• What is Radiation?
• What is Sound?
• Absolute Pressure
• What is a Joule?
• What is Mechanical Energy?
• What is Solar Energy?
• What is the Coriolis Effect?
• Boyle’s Law
• Concave Mirror
• First Law of Thermodynamics
• How Does a Compass Work?
• How Fast is Mach 1?
• Radioactive Dating
• Planck Time
• Charles’ Law
• Isaac Newton Inventions
• What is Conduction?
• Concave Lens
• Conductance
• Convex Lens
• Death Ray
• Nuclear Physics
• Double Slit Experiment
• Emissivity of Materials
• Radioisotope

Astronomy is a complex field that has slowly evolved to encompass several disciplines. An astronomer can not solely be a science person, they have to be techno-savvy, well written, and able to communicate well verbally. An astronomer has to be able to compel with empirical data and convincing verbage.

Here are a few facts about astronomy followed by a long list of links to as much information as you can handle on the topic.

Ancient astronomy was more of a branch of philosophy than real science. Astronomers had no way to directly observe any celestial bodies in detail, so had to make best guesses and then convince everyone else that they were right.

Before Copernicus came on the scene, astronomers believed that the Earth was the center of the Universe, the Sun and the ‘four’ planets orbited around it in a series of complex movements.

Did you know that despite the advent of space telescopes and launching many space probes, we have only observed a minor fraction of the known Universe? That doesn’t even take into account the Universe that we have no knowledge of at this time.

In the links below you will find a great deal of information about astronomy: some of the terminology used, images, and different discoveries made in the field. Hopefully, what you read will inspire you to delve even more deeply into the vastness of space.

• Plane of the Ecliptic
• Cherenkov Radiation
• Armillary Sphere
• Absolute Magnitude
• Ecliptic
• Astrolabe
• Greenwich Mean Time
• Infrared Spectroscopy
• Orrery
• Apparent Magnitude
• Retrograde
• Asterisms
• Stellar Parallax
• Celestial Body
• Conjunction
• Nucleosynthesis
• Cosmological Constant
• Roche Limit
• Ephemerides
• Eccentricity
• Lagrange Points
• Dark Matter
• Accretion
• Transit
• Hubble Constant
• Ptolemy Astronomy
• Right Ascension
• Chromatic Aberration

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There have been some big eruptions in recent history, like Mount Pinatubo, Mount St. Helens, and even Krakatoa. But those were tiny compared to some of the largest eruptions that have ever happened in the Earth’s history. So what was the largest eruption ever?

First, let’s get a sense of scale. When Krakatoa exploded in 1883, it released more than 21 cubic kilometers of rock, ash and pumice measuring 6 on the Volcanic Explosivity Index. At least 36,000 people died in the eruption and the tsunamis that followed.

Well, that was nothing.

Lake Toba in Indonesia measures 100 km long and 30 km wide and goes down to a depth of 505 meters. But it’s actually the collapsed caldera of a supernova that detonated about 74,000 years ago. Geologists believe that it erupted with an intensity of 8 on the Volcanic Explosivity Index, releasing 2,800 cubic kilometers of ash, rock and pumice. It deposited a layer of ash 15 centimeters thick over the entire Indian subcontinent.

Want bigger? No problem. The La Garita Caldera eruption in Colorado erupted about 28 million years ago, blasting out 5,000 cubic kilometers of ash.

We have written many articles about volcanoes for Universe Today. Here’s an article about supervolcanoes, and here’s an article about the Krakatoa eruption.

Want more resources on the Earth? Here’s a link to NASA’s Human Spaceflight page, and here’s NASA’s Visible Earth.

We have also recorded an episode of Astronomy Cast about Earth, as part of our tour through the Solar System – Episode 51: Earth.