Posted on by Jerry Coffey

When Was Mars Discovered?

This full-circle view from the panoramic camera (Pancam) on NASA's Mars Exploration Rover Spirit shows the terrain surrounding the location called "Troy," where Spirit became embedded in soft soil during the spring of 2009. Credit: NASA/JPL

[/caption]
It is impossible to know the answer to ”when was Mars discovered”. It is bright enough to be seen in the night sky without binoculars or a telescope and has been documented for at least 4,000 years.

If you were to change the question a little to ”who first theorized that Mars was a planet”, then an answer can be found. Nicolaus Copernicus is the first astronomer to postulate that Mars and a few other bodies known at the time were planets. The heliocentric theory that he published in 1543 marked the first time that astronomers widely considered the possibility that the Sun was the center of the Solar System instead of the Earth.

While no one knows who first discovered Mars, we do know who made many of the discoveries about the planet. It is known that Tycho Brahe, a Danish astronomer made accurate calculations of the position of Mars as early as 1576. Johannes Kepler theorized that the orbit of Mars was elliptical in contradiction to what astronomers believed at the time. He soon expanded that theory to encompass all planets. In 1659, Christian Huygens, a Dutch astronomer drew Mars with the observations he made using a telescope he designed himself. He also discovered a strange feature on the planet that became known as Syrtis Major.

On November 28, 1964, Mariner 4 was launched successfully on an eight-month voyage to the Red Planet. It made its first flyby on July 14, 1965, collecting the first close-up photographs of another planet. The pictures showed many impact craters, some of them touched with frost in the chill Martian evening. The Mariner 4 spacecraft was able to function for about three years in solar orbit, continuing long-term studies of the solar wind environment and making coordinated measurements with Mariner 5.

There are currently six spacecraft in orbit around Mars or on its surface and several more are in the planning or design stages. Five are gathering data at an amazing rate, the other(Phoenix) is non-functioning. New discoveries like subsurface water ice and methane plumes in the atmosphere are being made on a regular basis. Scientists may not be able to give an answer to ”when was Mars discovered”, but they can offer answers to thousands of other questions and the list is growing as we speak.

We have written many articles about the study of Mars. Here an article about how methane is being produced on Mars, and the possible discovery of life on Mars.

Here are some additional articles about the early observations of Mars, and here’s a whole book about observing Mars.

We have recorded an entire episode of Astronomy Cast about the planet Mars. Listen to it here, Episode 52: Mars.

Source: NASA

Posted on by Nancy Atkinson

After Loss of Lunar Orbiter, India Looks to Mars Mission

India Moon Mission
Artist concept of Chandrayaan-1 orbiting the moon. Credit: ISRO

[/caption]
After giving up on re-establishing contact with the Chandrayaan-1 lunar orbiter, Indian Space Research Organization (ISRO) Chairman G. Madhavan Nair announced the space agency hopes to launch its first mission to Mars sometime between 2013 and 2015. Nair said the termination of Chandrayaan-1, although sad, is not a setback and India will move ahead with its plans for the Chandrayaan-2 mission to land an unmanned rover on the moon’s surface to prospect for chemicals, and in four to six years launch a robotic mission to Mars.


“We have given a call for proposal to different scientific communities,” Nair told reporters. “Depending on the type of experiments they propose, we will be able to plan the mission. The mission is at conceptual stage and will be taken up after Chandrayaan-2.”

On the decision to quickly pull the plug on Chandrayaan-1, Nair said, “There was no possibility of retrieving it. (But) it was a great success. We could collect a large volume of data, including more than 70,000 images of the moon. In that sense, 95 percent of the objective was completed.”

Contact with Chandrayaan-1 may have been lost because its antenna rotated out of direct contact with Earth, ISRO officials said. Earlier this year, the spacecraft lost both its primary and back-up star sensors, which use the positions of stars to orient the spacecraft.

The loss of Chandrayaan-1 comes less than a week after the spacecraft’s orbit was adjusted to team up with NASA’s Lunar Reconnaissance Orbiter for a Bi-static radar experiment. During the maneuver, Chandrayaan-1 fired its radar beam into Erlanger Crater on the moon’s north pole. Both spacecraft listened for echoes that might indicate the presence of water ice – a precious resource for future lunar explorers. The results of that experiment have not yet been released.

Chandrayaan-1 craft was designed to orbit the moon for two years, but lasted 315 days. It will take about 1,000 days until it crashes to the lunar surface and is being tracked by the U.S. and Russia, ISRO said.

The Chandrayaan I had 11 payloads, including a terrain-mapping camera designed to create a three-dimensional atlas of the moon. It is also carrying mapping instruments for the European Space Agency, radiation-measuring equipment for the Bulgarian Academy of Sciences and two devices for NASA, including the radar instrument to assess mineral composition and look for ice deposits. India launched its first rocket in 1963 and first satellite in 1975. The country’s satellite program is one of the largest communication systems in the world.

Sources: New Scientist, Xinhuanet

Posted on by Nancy Atkinson

Future Designs: Robotic Mars Greenhouse, Teleporting Fridge

"Little Prince" robot greenhouse. Credit: Electrolux

[/caption]
Now THIS is what I’m talking about! Every year Electrolux holds a competition for students to design concepts for future appliances, and they’ve just announced the eight finalists. My favs: a robotic greenhouse for Mars and a teleporting refrigerator. Le Petit Prince (Little Prince) is a robotic greenhouse concept that is specially designed to help the future exploration and expanding population when we colonize Mars. This intelligent robot carries and cares for a plant inside its glass container, which is functionally mounted on a four-legged self-transporting pod. Not only does it search for the optimum place to receive enough sunlight and other nutrients, it also send reports of its movements and developments to its fellow greenhouse robots through wireless communication. It was designed by Martin Miklica, from the Brno University of Technology in the Czech Republic. He said he was inspired by the book The Naked Sun by Isaac Asimov and R2-D2 from Star Wars (and surely Wall-E had something to do with this, too.)

See video of Le Petit Prince, below, and of the teleporting fridge.

This one I can’t wait for: The Teleport Fridge by Dulyawat Wongnawa, Chulalongkorn University, Thailand. Once we figure out how to beam things up, the Teleport Fridge teleports food, eliminating the time and distance a person has to travel to buy fresh groceries or products from a store or farm. Using touch-screen technology as the interface for the teleportation process, the Teleport Fridge simply teleports food to compartments in its refrigeration and freezer units. If the food spoils, it teleports it to the compost pile. Very cool, but it takes the adventure out of opening those containers in the back of the fridge.

object width=”560″ height=”340″>

See the other six design concepts and vote for your favorite here.

Source: Electrolux Design Lab

Posted on by Nancy Atkinson

Mars Reconnissance Orbiter Goes Into Safe Mode Again

Artists concept of the Mars Reconnaisance Orbiter. Credit: NASA/JPL

[/caption]
NASA’s Mars Reconnaissance Orbiter put itself into a safe mode Wednesday morning, Aug. 26, for the fourth time this year. While in safe mode, the spacecraft can communicate normally with Earth, but aborts its scheduled activities, and awaits further instructions from ground controllers. “We hope to gain a better understanding of what is triggering these events and then have the spacecraft safely resume its study of Mars by next week,” said MRO Project Manager Jim Erickson.

Engineers have begun the process of diagnosing the problem prior to restoring the orbiter to normal science operations, a process expected to take several days. They will watch for engineering data from the spacecraft that might aid in identifying the cause of event and possibly of previous ones.

A possible cause for the frequent anomalies is cosmic ray hits. But the spacecraft has reacted differently with the various safe mode entries. The orbiter spontaneously rebooted its computer Wednesday, as it did in February and June, but did not switch to a redundant computer, as it did in early August.

To help in investigating a root cause of the three previous anomalies, engineers had programmed the spacecraft to frequently record engineering data onto non-volatile memory. That could give an improved record of spacecraft events leading up to the reboot.

MRO has been in Mars orbit since 2006, and has returned more data than all other current and past Mars missions combined.

Source: JPL

Posted on by Abby Cessna

Solar System Orbits

Take a look at the Solar System from above, and you can see that the planets make nice circular orbits around the Sun. But dwarf planet’s Pluto’s orbit is very different. It’s highly elliptical, traveling around the Sun in a squashed circle. And Pluto’s orbit is highly inclined, traveling at an angle of 17-degrees. This strange orbit gives Pluto some unusual characteristics, sometimes bringing it within the orbit of Neptune. Credit: NASA

[/caption]
One of the International Astronomical Union’s (IAU) requirements for a celestial body to be classified as a planet (or a dwarf planet) is that it orbits the Sun. All of the planets have different orbits, which affect many of the planets’ other characteristics.

Since Pluto became a dwarf planet, Mercury is the planet with the most eccentric orbit. The eccentricity of an orbit is the measurement of how different the orbit is from a circular shape. If an orbit is a perfect circle, its eccentricity is zero. As the orbit becomes more elliptical, the eccentricity increases. Mercury’s orbit ranges from 46 million kilometers from the Sun to 70 million kilometers from the Sun.

Venus, which is right next to Mercury, has the least eccentric orbit of any of the planet in the Solar System. Its orbit ranges between 107 million km and 109 million km from the Sun and has an eccentricity of .007 giving it a nearly perfect circle for its orbit.

Earth also has a relatively circular orbit with an eccentricity of .017. Earth has a perihelion of 147 million kilometers; the perihelion is the closest point to the Sun in an object’s orbit. Our planet has an aphelion of 152 million kilometers. An aphelion is the furthest point from the Sun in an object’s orbit.

Mars has one of the most eccentric orbits in our Solar System at .093. Its perihelion is 207 million kilometers, and it has an aphelion of 249 million kilometers.

Jupiter has a perihelion of 741 million kilometers and an aphelion of 778 million kilometers. Its eccentricity is .048. Jupiter takes 11.86 years to orbit the Sun. Although this seems a long time compared to the time our own planet takes to orbit, it is only a fraction of the time of some of the other planets’ orbits.

Saturn is 1.35 billion kilometers at its perihelion and 1.51 billion kilometers from the Sun at its furthest point. It has an eccentricity of .056. Since it was first discovered in 1610, Saturn has only orbited the Sun 13 times because it takes 29.7 years to orbit once.

Uranus is 2.75 billion miles from the Sun at its closest point and 3 billion miles from the Sun at its aphelion. It has an eccentricity of .047 and takes 84.3 years to orbit the Sun. Uranus has such an extreme axial tilt (97.8°) that rotates on its side. This causes radical changes in seasons.

Neptune is the furthest planet from the Sun with a perihelion of 4.45 billion kilometers and an aphelion of 4.55 billion kilometers. It has an eccentricity of .009, which is almost as low as Venus’ eccentricity. It takes Neptune 164.8 years to orbit the Sun.

Universe Today has articles on orbits of the planets and asteroid orbits.

For more information, check out articles on an overview of the Solar System and new planet orbits backwards.

Astronomy Cast has episodes on all the planets including Mercury.

References:
NASA: Transits of Mercury
NASA: Solar System Math
NASA: Mars, You’re So Complicated
NASA Solar System Exploration

Posted on by Nancy Atkinson

Watching Science in Action on Mars

This view of a rock called "Block Island," the largest meteorite yet found on Mars, comes from the panoramic camera (Pancam) on NASA's Mars Exploration Rover Opportunity. Credit: NASA/JPL

[/caption]
One of the great things about the Mars Exploration Rovers is that we get to see these scrappy little vehicles ramble across the surface of Mars, and watch science in action. Case in point: the meteorite found by Opportunity, dubbed “Block Island.” Scientists are debating all sorts of things about this watermelon-sized rock. How old is it? What is it made of? Where could it have come from? But not only are we learning about this alien rock, we’re also learning about the Red Planet itself and its environmental history.

See below for a new 3-D version of Block Island created by Stu Atkinson.

3-D Block Island created by Stuart Atkinson.
3-D Block Island created by Stuart Atkinson.

Scientists calculate Block Island is too massive to have hit the ground without disintegrating unless Mars had a much thicker atmosphere than it has now when the rock fell. An atmosphere slows the descent of meteorites, and with today’s thin Martian atmosphere, this heavy rock would have plummeted to the surface.

Block Island is approximately 60 centimeters (2 feet) in length, half that in height, probably weighs about a half ton, and has a bluish tint that distinguishes it from other rocks in the area.

Opportunity found a smaller iron-nickel meteorite, called “Heat Shield Rock,” in late 2004. Block Island is roughly 10 times as massive as Heat Shield Rock and several times too big to have landed intact without more braking than today’s Martian atmosphere could provide.

“Consideration of existing model results indicates a meteorite this size requires a thicker atmosphere,” said rover team member Matt Golombek of NASA’s Jet Propulsion Laboratory in Pasadena, Calif. “Either Mars has hidden reserves of carbon-dioxide ice that can supply large amounts of carbon-dioxide gas into the atmosphere during warm periods of more recent climate cycles, or Block Island fell billions of years ago.”

Additional studies also may provide clues about how weathering has affected the rock since it fell.

“There’s no question that it is an iron-nickel meteorite,” said Ralf Gellert of the University of Guelph in Ontario, Canada. Gellert is the lead scientist for the rover’s alpha particle X-ray spectrometer, an instrument on the arm used for identifying key elements in an object. “We already investigated several spots that showed elemental variations on the surface. This might tell us if and how the metal was altered since it landed on Mars.”

The triangular pattern of small ridges seen at the upper right in this image and elsewhere on the rock is characteristic of iron-nickel meteorites found on Earth, especially after they have been cut, polished and etched.
The triangular pattern of small ridges seen at the upper right in this image and elsewhere on the rock is characteristic of iron-nickel meteorites found on Earth, especially after they have been cut, polished and etched.

The microscopic imager on the arm revealed a distinctive triangular pattern in Block Island’s surface texture, matching a pattern common in iron-nickel meteorites found on Earth.

“Normally this pattern is exposed when the meteorite is cut, polished and etched with acid,” said Tim McCoy, a rover team member from the Smithsonian Institution in Washington. “Sometimes it shows up on the surface of meteorites that have been eroded by windblown sand in deserts, and that appears to be what we see with Block Island.”

Spectrometer observations have already identified variations in the composition of Block Island at different points on the rock’s surface. The differences could result from interaction of the rock with the Martian environment, where the metal becomes more rusted from weathering with longer exposures to water vapor or liquid.

“We have lots of iron-nickel meteorites on Earth. We’re using this meteorite as a way to study Mars,” said Albert Yen, a rover team member at JPL. “Before we drive away from Block Island, we intend to examine more targets on this rock where the images show variations in color and texture. We’re looking to see how extensively the rock surface has been altered, which helps us understand the history of the Martian climate since it fell.”

When the investigation of Block Island concludes, the team plans to resume driving Opportunity on a route from Victoria Crater, which the rover explored for two years, toward the much larger Endeavour Crater. Opportunity has covered about one-fifth of the 19-kilometer (12-mile) route plotted for safe travel to Endeavour since the rover left Victoria nearly a year ago.

Source: JPL

Posted on by Abby Cessna

Radius of the Planets

Size of the planets compared.

[/caption]

One way to measure the size of the planets is by radius. Radius is the measurement from the center of an object to the edge of it.

Mercury is the smallest planet with a radius of only 2,440 km at its equator. Mercury is not that much larger than the Moon, and it is actually smaller than some of our Solar System’s larger satellites, such as Titan. Despite Mercury’s small size, it is actually dense with higher gravity than you would expect for its size.

Venus has a radius of 6,052 kilometers, which is only a few hundred kilometers smaller than Earth’s radius. Most planets have a radius that is different at the equator than it is at the poles because the planets spin so fast that they flatten out at the poles. Venus has the same diameter at the poles and at the equator though because it spins so slowly.

Earth is the largest of the four inner planets with a radius of 6,378 kilometers at the equator. This is over two times larger than the radius of Mercury. The radius between the poles is 21.3 km less than the radius at the equator because the planet has flattened slightly since it only takes 24 hours to rotate.

Mars is a surprisingly small planet with a radius of 3,396 kilometers at the equator and 3,376 kilometers at the poles. This means that Mars’ radius is only about half of Earth’s radius.

Jupiter is the largest of all the planets. It has a radius of 71,492 kilometers at the equator and a radius of 66,854 kilometers at the poles. This is a difference of 4,638 kilometers, which is almost twice Mercury’s radius. Jupiter has a radius at the equator 11.2 times Earth’s equatorial radius.

Saturn has an equatorial radius of 60,268 kilometers and a radius of 54,364 kilometers at the poles making it the second largest planet in our Solar System. The difference between its two radiuses is a little more than twice the radius of Mercury.

Uranus has an equatorial radius of 25,559 kilometers and a radius of 24,973 kilometers at the poles. Although this is much smaller than Jupiter’s radius, it is around four times the size of Earth’s radius.

Neptune’s equatorial radius of 24,764 kilometers makes it the smallest of the four outer planets. The planet has a radius of 24,341 kilometers at the poles. Neptune’s radius is almost four times the size of Earth’s radius, but it is only about a third of Jupiter’s radius.

Universe Today has articles on the radius of Neptune and the size of the planets.

If you are looking for more information, check out NASA’s Solar System exploration page, and here’s a link to NASA’s Solar System Simulator.

Astronomy Cast has an episode on Venus and more on all the planets.

Posted on by Abby Cessna

Volume of the Planets

Planets and other objects in our Solar System. Credit: NASA.

[/caption]

There are a number of measurements that astronomers use, including mass, surface area, diameter, and radius, to determine the the size of the planets. Volume is one measurement of the size of a planet. It is a measurement of how much three-dimensional space an object occupies. The volumes of the planets, along with other measurements, help astronomers discover the physical composition of the planets in addition to other information about them.

Mercury is the littlest planet in our Solar System with the smallest volume of any planet. It has a volume of 6.083 x 1010 cubic kilometers, which is only 5.4% of Earth’s volume.

Venus is only slightly smaller than Earth with a volume of 9.38 x 1011 km3. That is 86% of the Earth’s volume. This may not seem like Venus is that close in size to our planet,  but Venus is closer in size to Earth than any other planet is.

Earth is the largest of the four inner planets, although it is nothing compared to the gas giants. Earth has a volume of 1.08 x 1012 cubic kilometers.

Mars is actually a rather small planet with a volume of 1.6 x 1011 cubic kilometers. While that is larger than Mercury’s volume and pretty big in general, it is only 15% of Earth’s volume. You could put over six planets the size of Mars inside the Earth.

The largest planet in our Solar System, Jupiter’s size is astounding. Jupiter has a volume of 1.43 x 1015 cubic kilometers. To show what this number means, you could fit 1321 Earths inside of Jupiter. It is hard to imagine how large that actually is.

Saturn is the second largest planet in the Solar System. It has a volume of 8.27 x 1014 cubic km. Although it is only a fraction of the size of Jupiter, you could fit 764 Earths inside of the gas giant.

Uranus is a large planet with a volume of 6.833 x 1013 cubic kilometers. You could fit a little more than 63 Earths inside of Uranus, but like the other gas giants, it is not very dense. Comprised mostly of gas, the planet is only about 14.5 times more massive than Earth is.

Neptune is the smallest gas giant in our Solar System, but it is still much larger than any of the inner planets. Neptune has a volume of 6.3 x 1013 cubic kilometers, which is equal to about 57 Earths. Even though Neptune’s volume is much greater than the Earth’s is, the gravity on Neptune is only about 14% greater than it is on Earth. This is due to the gas giant’s small mass.

Universe Today has articles on size of the planets and mass of the planets.

Check out an overview of the Solar System and all about the planets.

Astronomy Cast has an episode on Jupiter and episodes on all the planets.

Posted on by Abby Cessna

Mythology of the Planets

Planets and other objects in our Solar System. Credit: NASA.

[/caption]

Thousands of years ago, ancient civilizations turned to the heavens, marveling at their wonders. These ancient people worshipped various gods and often linked their gods with planets in the sky, which they considered to be “wandering stars.”

Mercury gets its name from the winged messenger of the gods. He was also the god of thievery, commerce, and travel. Most likely, the planet got its name from the rate at which it spins.

Venus was the Roman goddess of love and beauty, so it is a fitting name for this brightly shining planet. The only objects in our Solar System brighter than Venus are the Sun and the Moon. Ancient civilizations thought that Venus was two different objects – the Morning Star and the Evening Star. Other civilizations have also associated the planet with love. The Babylonians called the planet Ishtar after their goddess of womanhood and love.

Earth is the only planet not named after a Roman god or goddess, but it is associated with the goddess Terra Mater (Gaea to the Greeks). In mythology, she was the first goddess on Earth and the mother of Uranus. The name Earth comes from Old English and Germanic. It is derived from “eor(th)e” and “ertha,” which mean “ground.” Other civilizations all over the world also developed terms for our planet.

Mars is named after the Roman god of war. The planet got its name from the fact that it is the color of blood.  Other civilizations also named the planets for its red color.

Jupiter was the Roman king of the gods. Considering that Jupiter is the largest planet in our Solar System, it makes sense that the planet was named after the most important god.

Saturn was named after the Roman god of agriculture and harvest. While the planet may have gotten its name from its golden color, like a field of wheat, it also had to do with its position in the sky. According to mythology, the god Saturn stole the position of king of the gods from his father Uranus. The throne was then stolen by Jupiter.

Uranus was not discovered until the 1800’s, but the astronomers in that time period continued the tradition of naming planets after Roman gods. In mythology, Uranus was the father of Saturn and was at one time the king of the gods.

While Neptune almost ended up being named after one of the astronomers credited with discovering it – Verrier – that was greatly disputed, so it was named after the god of the sea. The name was probably inspired by its blue color.

Pluto is no longer a planet, but it used to be. The dark, cold, former planet was named after the god of the underworld. The first two letters of Pluto are also the initials of the man who predicted  its existence, Percival Lowell.

Universe Today has articles on names of the planets and all the planets.

For more information on the planets check out all about the planets and mythology of the planets.

Astronomy Cast has episodes on all the planets including Saturn.

Posted on by Abby Cessna

Surface of the Planets

Planets and other objects in our Solar System. Credit: NASA.

[/caption]

People have been intrigued for centuries by whether life could exist on other planets. While we now know that it is very unlikely that life as we know it could exist on other planets in our Solar System, many people do not know the surface conditions of these various planets.

Mercury resembles nothing so much as a larger version of the Moon. This planet is so close to the Sun that it is actually difficult to observe. The Hubble Space Telescope cannot look at it because it would permanently damage the lens.

Venus’ atmosphere of thick, toxic clouds hides the planet’s surface from view. Scientists and amateurs alike used to think that the planet was covered with thick forests and flora like tropical rainforests on Earth.  When they were finally able to send probes to the planet, they discovered that Venus’ surface was actually more like a vision of hell with a burning landscape that is dotted with volcanoes.

Mars has very diverse terrain. One of the planet’s most famous features is its canals, which early astronomers believed were “man”-made and contained water. These huge canyons were most likely formed by the planet’s crust splitting. Mars is also famous for its red color, which is iron oxide (rust) dust that covers the surface of the entire planet. The surface of Mars is covered with craters, volcanoes, and plains. The largest volcanoes of any planet are on Mars.

Jupiter is a gas giant, so it has no solid surface just a core of liquid metals. Astronomers have created a definition for the surface – the point at which the atmosphere’s pressure is one bar. This region is the lower part of the atmosphere where there are clouds of ammonia ice.

Saturn is also a gas giant so it has no solid surface only varying densities of gas. Like Jupiter, almost all of Saturn is composed of hydrogen with some helium and other elements in trace amounts.

Uranus and Neptune are also gas giants, but they belong to the subcategory of ice giants because of the “ices” in their atmospheres. Uranus’ surface gets its blue color from the methane in the atmosphere. Methane absorbs light that is red or similar to red on the color spectrum leaving only the light near the blue end of the spectrum visible.

Neptune is also blue due to the methane in its atmosphere. Its “surface” has the fastest winds of any planet in the Solar System at up to 2,100 kilometers per hour.

Universe Today has a number of articles including surface of Mars and surface of Mercury.

Check out NASA’s Solar System exploration page, and here’s a link to NASA’s Solar System Simulator.

Astronomy Cast has an episode on each planet including Earth.