Transit Of Venus In 2012

Comparison of the planets of the solar system, Pluto and Sun in relation to the earth.

Images: commons.wikimedia (Sun: Alan Friedman)

On this day, but in 1974 the NASA spacecraft Mariner 10 made its closest approach to Venus.

Credit: NASA / Mariner 10

Venus, viewed through violet and near-infrared filters.

Ten interesting facts about Mars

The ancient Sumerians believed that Mars was Nergal, the god of war and plague. During Sumerian times, Nergal was a minor deity of little significance, but, during later times, his main cult center was the city of Nineveh. In Mesopotamian texts, Mars is referred to as the “star of judgement of the fate of the dead”. The existence of Mars as a wandering object in the night sky was recorded by the ancient Egyptian astronomers and, by 1534 BCE, they were familiar with the retrograde motion of the planet. By the period of the Neo-Babylonian Empire, the Babylonian astronomers were making regular records of the positions of the planets and systematic observations of their behavior. For Mars, they knew that the planet made 37 synodic periods, or 42 circuits of the zodiac, every 79 years. They invented arithmetic methods for making minor corrections to the predicted positions of the planets.

Mars is the fourth planet from the Sun and the second-smallest planet in the Solar System after Mercury.

The bright rust color Mars is known for is due to iron-rich minerals in its regolith — the loose dust and rock covering its surface. The soil of Earth is a kind of regolith, albeit one loaded with organic content. According to NASA, the iron minerals oxidize, or rust, causing the soil to look red.

The rotational period and seasonal cycles of Mars are likewise similar to those of Earth, as is the tilt that produces the seasons. Mars is the site of Olympus Mons, the largest volcano and second-highest known mountain in the Solar System, and of Valles Marineris, one of the largest canyons in the Solar System.

Mars has two moons, Phobos and Deimos, which are small and irregularly shaped. These may be captured asteroids, similar to 5261 Eureka, a Mars trojan.

There are ongoing investigations assessing the past habitability potential of Mars, as well as the possibility of extant life. Future astrobiology missions are planned, including the Mars 2020 and ExoMars rovers. Liquid water cannot exist on the surface of Mars due to low atmospheric pressure, which is less than 1% of the Earth’s, except at the lowest elevations for short periods. The two polar ice caps appear to be made largely of water. The volume of water ice in the south polar ice cap, if melted, would be sufficient to cover the entire planetary surface to a depth of 11 meters (36 ft). In November 2016, NASA reported finding a large amount of underground ice in the Utopia Planitia region of Mars. The volume of water detected has been estimated to be equivalent to the volume of water in Lake Superior.

Mars can easily be seen from Earth with the naked eye, as can its reddish coloring. Its apparent magnitude reaches −2.91, which is surpassed only by Jupiter, Venus, the Moon, and the Sun. Optical ground-based telescopes are typically limited to resolving features about 300 kilometers (190 mi) across when Earth and Mars are closest because of Earth’s atmosphere.

Like Earth, Mars has differentiated into a dense metallic core overlaid by less dense materials. Current models of its interior imply a core with a radius of about 1,794 ± 65 kilometers (1,115 ± 40 mi), consisting primarily of iron and nickel with about 16–17% sulfur. This iron(II) sulfide core is thought to be twice as rich in lighter elements as Earth’s. The core is surrounded by a silicate mantle that formed many of the tectonic and volcanic features on the planet, but it appears to be dormant. Besides silicon and oxygen, the most abundant elements in the Martian crust are iron, magnesium, aluminum, calcium, and potassium. The average thickness of the planet’s crust is about 50 km (31 mi), with a maximum thickness of 125 km (78 mi). Earth’s crust averages 40 km (25 mi).

Mars lost its magnetosphere 4 billion years ago, possibly because of numerous asteroid strikes, so the solar wind interacts directly with the Martian ionosphere, lowering the atmospheric density by stripping away atoms from the outer layer. Both Mars Global Surveyor and Mars Expresshave detected ionised atmospheric particles trailing off into space behind Mars, and this atmospheric loss is being studied by the MAVEN orbiter. Compared to Earth, the atmosphere of Mars is quite rarefied.

Mars’s average distance from the Sun is roughly 230 million kilometres (143,000,000 mi), and its orbital period is 687 (Earth) days. The solar day (or sol) on Mars is only slightly longer than an Earth day: 24 hours, 39 minutes, and 35.244 seconds. A Martian year is equal to 1.8809 Earth years, or 1 year, 320 days, and 18.2 hours

Mars is scarred by a number of impact craters: a total of 43,000 craters with a diameter of 5 km (3.1 mi) or greater have been found. The largest confirmed of these is the Hellas impact basin, a light albedo feature clearly visible from Earth. Due to the smaller mass of Mars, the probability of an object colliding with the planet is about half that of Earth. Mars is located closer to the asteroid belt, so it has an increased chance of being struck by materials from that source. Mars is more likely to be struck by short-period comets, i.e., those that lie within the orbit of Jupiter. In spite of this, there are far fewer craters on Mars compared with the Moon, because the atmosphere of Mars provides protection against small meteors and surface modifying processes have erased some craters.

Martian craters can have a morphology that suggests the ground became wet after the meteor impacted.

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images: NASA/JPL-Caltech/Univ. of Arizona , ESA, Tunç Tezel

astronomy facts

Solar System: Things to Know This Week

Go for Venus! Fifty-five years ago this week, Mariner 2, the first fully successful mission to explore another planet launched from Cape Canaveral in Florida. Here are 10 things to know about Mariner 2.

1. Interplanetary Cruise 

On August 27, 1962, Mariner 2 launched on a three and a half month journey to Venus. The little spacecraft flew within 22,000 miles (about 35,000 kilometers) of the planet. 

2. Quick Study 

Mariner 2’s scan of Venus lasted only 42 minutes. And, like most of our visits to new places, the mission rewrote the books on what we know about Earth’s sister planet.

3. Hot Planet 

The spacecraft showed that surface temperature on Venus was hot enough to melt lead: at least 797 degrees Fahrenheit (425 degrees Celsius) on both the day and night sides.

4. Continuous Clouds 

The clouds that make Venus shine so bright in Earth’s skies are dozens of miles thick and permanent. It’s always cloudy on Venus, and the thick clouds trap heat - contributing to a runaway “greenhouse effect.”

5. Night Light 

Those clouds are why Venus shines so brightly in Earth’s night sky. The clouds reflect and scatter sunlight, making Venus second only to our Moon in celestial brightness.

6. Under Pressure 

Venus’ clouds also create crushing pressure. Mariner 2’s scan revealed pressure on the surface of Venus is equal to pressure thousands of feet under Earth’s deepest oceans.

7. Slow Turn 

Mariner 2 found Venus rotates very slowly, and in the opposite direction of most planets in our solar system.

8. Space Travel Is Tough 

Mariner 2 was a remarkable accomplishment, considering that in 1962 engineers were still in the very early stages of figuring out how operate spacecraft beyond Earth orbit. The first five interplanetary missions launched - by the U.S. and Soviet Union, the only two spacefaring nations at the time - were unsuccessful.

9. Not Ready for Its Close Up 

Mariner 2 carried no cameras. The first close-up pictures of Venus came from NASA’s Mariner 10 in 1974.  

10. Hot Shot 

The first (and still incredibly rare) photo of the surface of Venus was taken by the Soviet Venera 9 lander, which survived for a little more than a minute under the crushing pressure and intense heat on the ground.

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Venus adores the moon by littletinperson on Flickr.

(NASA)  Venus at Night in Infrared from Akatsuki

Image Credit: JAXA, ISAS, DARTS; Processing & Copyright: Damia Bouic

Why is Venus so different from Earth? To help find out, Japan launched the robotic Akatsuki spacecraft which entered orbit around Venus late in 2015 after an unplanned five-year adventure around the inner Solar System. Even though Akatsuki was past its original planned lifetime, the spacecraft and instruments were operating so well that much of its original mission was reinstated. Also known as the Venus Climate Orbiter, Akatsuki’s instruments investigated unknowns about Earth’s sister planet, including whether volcanoes are still active, whether lightning occurs in the dense atmosphere, and why wind speeds greatly exceed the planet’s rotation speed. In the featured image taken by Akatsuki’s IR2 camera, Venus’s night side shows a jagged-edged equatorial band of high dark clouds absorbing infrared light from hotter layers deeper in Venus’ atmosphere. The bright orange and black stripe on the upper right is a false digital artifact that covers part of the much brighter day side of Venus. Analyses of Akatsuki images and data has shown that Venus has equatorial jet similar to Earth’s jet stream.

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The sky seemed to smile over much of planet Earth. Visible the world over was an unusual superposition of our Moon and the planets Venus and Jupiter. A crescent Moon over Los Angeles appears to be a smile when paired with the planetary conjunction of seemingly nearby Jupiter and Venus.

“Anyone who has never made a mistake has never tried anything new.” - Albert Einstein