Universe Today

June 29, 2009December 24, 2015 by Fraser Cain

How Long Does it Take to Get to Mercury?

The MESSENGER spacecraft at Mercury (NASA)

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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

June 29, 2009December 24, 2015 by Fraser Cain

Closest Planet to Mercury

A different side of Mercury. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

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What is the closest planet to Mercury? As you probably know, Mercury is the closest planet to the Sun, orbiting at an average distance of 57.9 million km. So then, what planet gets closest to Mercury in orbit.

The answer, of course is Venus, the 2nd closest planet to the Sun. Venus orbits at an average distance of 108.2 million km. So, how close can Mercury and Venus get? Well when I said that Mercury orbits at 57.9 million km, that’s actually an average. Mercury follows an elliptical orbit around the Sun. At its closest point, Mercury gets to within 46 million km, and then at its most distant point, it gets to be 69.8 million km.

And Venus also travels in an elliptical orbit, varying between 107.4 million km and 108.9 million km. So, when the two planets are closest to one another in orbit, the distance between them is about 37.6 million km. And at their most distant point, they can get to be 178.7 million km.

Can Earth ever be closer to Mercury than Venus? Earth’s orbit ranges between 147.1 and 152.1 million km. So when Earth and Mercury are at their closest point, they’re only separated by 77.3 million km. What this means is that there are times when Earth is actually closer to Mercury than Venus; although, most of the time, Venus is the closest planet.

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.

Más cercano al planeta Mercurio

June 29, 2009December 24, 2015 by Abby Cessna

The Brightest Planet

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When you look up into the sky, if you are lucky, you see shining stars on a field of blue-black. Not all of these objects are stars though. Venus, which can be seen with the unaided eye from Earth, is the brightest planet in our Solar System. Venus was given the nickname evening star and morning star because of its bright, consistent presence. It is often called Earth’s twin because it is similar in shape and size to our own planet. The only objects brighter than Venus are the Moon and the Sun. Sirius, the brightest star that can be seen in the sky, is much dimmer than Venus is. People have known that Venus existed for centuries. The planet was named after the Roman goddess of love and this shining planet has long been associated with femininity.

A planet’s brightness is determined by how much light is reflected by the planet. The term albedo refers to the balance between how much light is absorbed and how much light is reflected by the planet. As the brightest planet, Venus has a very high albedo. Seventy percent of the light that hits Venus is reflected back into space. Why does Venus have such a high albedo though? There are droplets of sulfuric acid and acidic crystals in the atmosphere of Venus. The smooth surfaces of these droplets of sulfuric acid and crystals reflect light very well, which is one reason why Venus is so bright. There is a lot more to this planet than its shimmering appearance though.

The same atmosphere that causes Venus to shine like a beacon also prevents us from getting a look at the planet’s surface. Astronomers did not know what the planet looked like until probes checked out the surface in the last few decades. Because the surface of Venus could not be seen, scientists and writers imagined that it was a tropical, lush landscape. That was not the case though. In addition to hiding the surface and reflecting light, Venus’ atmosphere traps heat from the Sun, turning the planet into a raging furnace. Reaching temperatures of over 460°C, Venus is the hottest planet in the Solar System. Its landscape is similar to that of Mercury and the Moon – rocky, barren terrain with no sign of life. Venus has long enchanted viewers with its beauty and shining presence. Try looking for this planet in the sky; you may find yourself captivated by this shining beauty like many before you.

Universe Today has many articles on Venus including the atmosphere of Venus and how to find Venus in the sky.

For more information check out these articles from NASA on an overview of Venus and from Nine Planets on the brightest planet.

Astronomy Cast has an episode on Venus you should take a look at.

June 29, 2009December 24, 2015 by Fraser Cain

Physics

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!

June 29, 2009December 24, 2015 by Nancy Atkinson

First Conclusive Signature for Lunar Uranium

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Using data obtained from the gamma ray spectrometer on the Kaguya spacecraft scientists have found signatures of uranium, an element not seen in previous moon-mapping efforts. In addition to uranium, the Kaguya GRS data also is showing clear signatures for thorium, potassium, oxygen, magnesium, silicon, calcium, titanium and iron.

“We’ve already gotten uranium results, which have never been reported before,” said Robert C. Reedy, senior scientists at the Planetary Science Institute. “We’re getting more new elements and refining and confirming results found on the old maps.”

Earlier gamma-ray spectrometer maps from the Apollo and Lunar Prospector missions show a few of the moon’s chemical elements. But the maps constructed by Reedy and the Kaguya GRS team — using data gathered by state-of-the-art high-energy-resolution germanium detectors — are extending the earlier results and improving our understanding of the moon’s surface composition.

Reedy and his colleagues are using measurements from the Kaguya lunar orbiter’s GRS to construct high-quality maps of as many chemical elements as possible. Kaguya was launched in September 2007 and crashed into the moon at the end of its mission on June 10 of this year.

Source: Planetary Science Institute

June 29, 2009December 24, 2015 by Nancy Atkinson

Watch Live Webcast of Ulysses Spacecraft Switch-off

Artist impression of the Ulysses spacecraft. Credit: NASA/ESA

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UPDATE: Use this link to watch the webcast (the other one isn’t working very well!)

It’s the spacecraft that just won’t quit. We ran a story about a year ago that the Ulysses spacecraft was dying of natural causes (running out of power to keep the spacecraft warm and functional) and its mission would likely end by July 1, 2008. The thing is, the spacecraft just kept hanging on…and hanging on….and hanging on. But now, after 18.6 years in space and defying several earlier expectations of its demise, Ulysses will finally be switched off. You can watch a live webcast of the final communication with the spacecraft, which will occur on June 30, 2009, starting at 15:35 GMT and go until 20:20 GMT.

“Ulysses has taught us far more than we ever expected about the Sun and the way it interacts with the space surrounding it,” said Richard Marsden, ESA’s Ulysses Project Scientist and Mission Manager.

Ulysses was the first spacecraft to survey the environment in space above and below the poles of the Sun in the four dimensions of space and time. Among many other ground-breaking results, the mission showed that the Sun’s magnetic field is carried into the Solar System in a more complicated manner than previously believed. Particles expelled by the Sun from low latitudes can climb up to high latitudes and vice versa, even unexpectedly finding their way down to planets.

And as a eulogy to the Ulysses spacecraft, here’s the last lines from the poem “Ulysses” by English poet Alfred, Lord Tennyson:

“Death closes all; but something ere the end,
Some work of noble note, may yet be done…
‘Tis not too late to seek a newer world…
To sail beyond the sunset.”

Link for webcast.

June 29, 2009December 24, 2015 by Mark Mortimer

Book Review: Keep Watching the Skies

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We work hard to put food on the table and a roof over our heads. If lucky, we’ve got some time left over for other activities. Patrick McCray’s book “Keep Watching the Skies – The Story of Operation Moonwatch and the Dawn of the Space Age” is the story of a program that took advantage of some of those spare hours. During its time, this program had people encouraged, organized, and trained to view the skies and contribute to the nascent space age.

In McCray’s book, the reader gets transported back to the heady days of the mid 1950s when anything seemed possible. Martians could land, asteroids could impact and enemies could lob projectiles across the skies. But, governments had no capability and scientists had no clue as to how to detect any intransigencies. Hence, the call went out for civilian volunteers to watch for transits. With enough volunteers spread across the world, then we’d have the ability to know where, when and perhaps what has briefly streaked across the inky blackness.

As a well written book by an historian, there’s lots of interesting detail within. McCray lays out the basis for the Moonwatch program by including many references to the global politics of the day, whether McCarthyism or socialism. In addition, he gives a cross section of societal attitudes, principally being civic duty and a near adoration of science and technology. Expanding upon this, he goes into the personalities: especially Fred Whipple of the Smithsonian Astrophysical Observatory who set the basis for the program, Len Campbell who acted as the voice of the program, and the many volunteers, such as Vioalle Hefferean who used their time and abilities to scan the skies. Out of this mix comes an entertaining and detailed assessment of everyday talents and the enthusiastic amateurs who were so enthralled with the safety of their nation and contributing to hard science.

This later concept overrides the theme of the book. Though the book is principally a review of a scientific program, it’s also a valuable insight into how amateurs and professionals relate. For instance, some amateurs showed their capabilities to be as good as or better than the professionals. And some professionals wouldn’t support amateurs, no matter how beneficial. As such, this book can provide a reader with some significant insight into the interactions of these elements of society. Also, it shows a fascinating change from almost universal public support for technology toward disregard or disfavour. In it, the reader sees just how flighty public support really is. But, as a history of the little known Operation Moonwatch, this book makes a pleasant, detailed and well referenced story.

The dawn of the space age brought a whole new realm of space science immediately and forcefully into people’s consciousness. Some rebelled at this new perspective, but many were drawn into this wondrous realm. In Patrick McCray’s book “Keep Watching the Skies – The Story of Operation Moonwatch and the Dawn of the Space Age“, this scientific field gets shown for the pure delight that could be derived from participating and contributing even without being a scientist.

June 29, 2009April 26, 2016 by Nancy Atkinson

Landforms Indicate “Recent” Warm Weather on Mars

Retrogressive scarps with cuspate niches, long branching spurs and associated fluvial-like tributary channels. Credit:NASA/JPL/UofA

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Remember the polygon-shaped landforms at Mars north polar region that the Phoenix lander studied? The polygons are produced by seasonal expansion and contraction of ground ice, and these shapes have been found in other regions on Mars as well. New studies of images from the HiRISE camera on the Mars Reconnaissance Orbiter indicates that the Martian surface near the equator experienced freeze-thaw cycles as recently as 2 million years ago. This means Mars had significantly warmer weather in its recent past, and has not been locked in permafrost conditions for billions of years as had been previously thought.

The HiRISE images show polygon-patterned surfaces, branched channels, blocky debris and mound/cone structures.

Dr. Matthew Balme, from The Open University, made the new discovery by studying detailed images of equatorial landforms that formed by melting of ice-rich soils, such as the polygons, branched channels, blocky debris and mound/cone structures. These are all found in an outflow channel, thought to have been active as recently as 2 million to 8 million years ago. Since the landforms exist within, and cut across, the pre-existing features of the channel, this suggests that they, too, were created within this timeframe.

Full resolution view of domed polygons from HiRISE. Credit: NASA/JPL/U of A

All of these features are similar to landforms on Earth typical of areas where permafrost terrain is melting.

“The features of this terrain were previously interpreted to be the result of volcanic processes,” said Balme. “The amazingly detailed images from HiRISE show that the features are instead caused by the expansion and contraction of ice, and by thawing of ice-rich ground. This all suggests a very different climate to what we see today.”

This also means as the shorter the time period since the last warm weather on the planet, the better the chance that any organisms that may have lived in warmer times are still alive under the planet’s surface.

“These observations demonstrate not only that there was ice near the Martian equator in the last few million years, but also that the ice melted to form liquid water and then refroze,” said Balme. “And this probably happened for many cycles. Given that liquid water seems to be essential for life, these kinds of environments could be a great place to look for evidence of past life on Mars.”

Source: STFC

June 28, 2009December 24, 2015 by Mark Mortimer

Book Review: How To Live On Mars

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With all the probes recently landing on Mars, it’s no wonder we feel that the planet is close enough to vacation there. Robert Zubrin has such a scheme already in place for his book entitled “How to Live on Mars – A Trusty Guidebook to Surviving and Thriving on the Red Planet“. Though vacationers are welcome, he much more expects the arrival of immigrants who are ready and raring to put spade into ground for a homestead of the future.

Even though people have yet to land on Mars, our probes peer down, crawl upon and drill into all parts of the Martian surface. From them, we’ve a good understanding of the atmospheric make-up, the surface composition and likely sub-surface material. And, results indicate that people could exist on that planet, but it would be anything other than a comfortable existence. At least at the beginning.

Though the future’s not certain, Zubrin’s book takes the possibly optimistic view of a wise Martian resident providing glimmers of hope for new immigrants. Using an active, present tense, his book dollops up words and ideas of wisdom, such as selecting an appropriate space suit, deciding on the best location for a space hab, and fine-stepping through bureaucratic shenanigans. A humorous slant on the decision making and a slight bend toward technical details make the reading fun and informative. Occasionally, the reader may forget that the book’s proverbial vantage point occurs sometime about a hundred years in the future.

Were this book only providing a light and possible view of human activities in the future, it would have made for a very enjoyable read. But, Zubrin can’t seem to resist throwing darts and arrows at apparently favourite targets of NASA, big business and government bureaucracy. An occasional jab would have grounded the book into mainstream opinion. But, Zubrin takes every issue in the guide book and glamorizes his decision at the expense of “the charlatans of NASA” and corrupt governments. Thus, even though the perspective is from the future, the book seems a critique of the present.

Yet, Zubrin has a lot of experience in the space field, including living at a Mars analog. This experience comes alive in the book, whether from the viewpoint of people on Mars who soar with flying chickens or who safe habitation modules from marauding goats. And yes, with a lot of people on Mars, there will be need for governments and some corruption will likely exist. After all people aren’t perfect. But, we still have to get there, and reading this book may help place us all a little closer to living upon that not so far away planet.

Once we have the vehicles to carry our bodies to Mars and once a substantial number of people live there, then we will need guidebooks on how the rest of us can join in. Though perhaps jumping the gun a bit, Robert Zubrin’s book “How to Live on Mars – A Trusty Guidebook to Surviving and Thriving on the Red Planet” presents one particular view on people’s needs to living on that little red speck that we see in the night sky. Perhaps with more people imagining our presence there, then we won’t have to wait so long for the eventuality to occur.

June 27, 2009December 16, 2015 by Stephanie Bender

What is the Lithosphere?

The Earth's layers (strata) shown to scale. Credit: pubs.usgs.gov

According to the United States Geological Survey (the USGS), the lithosphere is, “the solid outer zone of the Earth comprising the crust and the upper layer of the mantle.”

Also, according to the USGS, the term comes from the Greek word, lithos, meaning, rock, and the word, sphere, which can be any round object, such as a ball, an orange, or, even, you guessed it, a planet.

Wasn’t that helpful? To a Geologist, a scientist who studies the Earth, maybe; but, for us mere mortals, not really. When I think of, “Crust,” I think of the top of a pie. Apple’s my favorite, but anyway, back to the topic. Other times, I think of a loaf of fresh-baked, piping-hot bread, right out of the oven, smothered with honey butter. Oh, it’s so good! Wait a minute! What am I doing? OK, OK, let me make this point so I can forget about food.

When we discuss, “The Earth’s crust,” we’re talking about the outer layer of the Earth’s surface. This is part of the lithosphere. The crust’s made from 3 different types of rock: Igneous; sedimentary; and, metamorphic. Igneous rock forms when cracks in the Earth, known as fissures, break open or a volcano erupts. Both events bring hot, molten rock, known as magma, to the surface, where it cools and becomes different types of rock; what types may depend upon what else mixes with it, how much pressure it’s under, or how much time passes.

The magma, comes from the other part of the lithosphere. It’s released from the upper portion of the mantle. The lithosphere’s responsible for the renewal of the Earth’s surface. When the magma’s released, it becomes known as lava. Other types of rock might be present when the lava arrives; and, since intense heat, pressure, or both can change the rocks from to another, the crust might appear very different afterwords. Some rocks are melted down entirely, and their molten remains may return to the mantle. Eventually, those remains will make another appearance; but, when, or in what form, when all is said and done, who can say?

The lithosphere is very important to the rock cycle. Without it, our planet wouldn’t change. I remember the horrible eruption of Mount St. Helens. The devastation, looked like pictures from Japan, after the atomic bombs hit Hiroshima and Nagasaki; but, I recall hearing later that scientists discovered never-before-seen plant life due to the changes the particles underwent from the pressure, high heat, iron content, and their quick ability to adapt. Like our hearts, the lithosphere keeps our Earth young and healthy.

Universe Today has some other great articles, if you want to learn more about this or similar subjects. One excellent resource is, Earth, Barely Habitable?. Another is, Interesting Facts About Planet Earth.