First map of Earth’s hidden groundwater reserves shows we’re using them too quickly

Modern-groundwater-map-printx_1024.jpgAn international team of hydrologists has come up with the best estimate yet for Earth’s total supply of groundwater, saying that nearly 23 million cubic kilometers of groundwater is contained in hidden reserves under the surface of the planet. And while that might sound like a lot, it’s not enough to sustain us if we keep consuming it as fast as we are right now.

The study suggests that less than 6 percent of groundwater in the upper 2 kilometers of the Earth’s landmass is renewable within a human lifetime. That statistic is concerning, not only because the uppermost water is what we can access for drinking, but also because the lengthy renewal cycle is slower than our consumption habits.

“This has never been known before,” said lead researcher Tom Gleeson of the University of Victoria in Canada. “We already know that water levels in lots of aquifers are dropping. We’re using our groundwater resources too fast – faster than they’re being renewed.”

To come up with their global groundwater map, the researchers compiled multiple data-sets, including data from almost a million watersheds and more than 40,000 groundwater models. Of the nearly 23 million cubic kilometers of total groundwater on the planet, approximately 0.35 million cubic kilometers is younger than 50 years old.

The distinction between young and old groundwater is important. Young (or modern) groundwater lies closer to the surface and is more likely to be drinkable. In comparison, older groundwater – which can date as far back as millions of years – lies deeper in Earth’s landmass, and may contain arsenic or uranium. It’s often stagnant and saltier than seawater, and as such, is only usually suitable for agricultural or industrial purposes.

Young groundwater’s proximity to the surface means it’s easier for us to access it and also easier to renew with fresh rainwater – but it’s also more readily exposed to human contamination and more vulnerable to environmental risks like climate change.

The researchers’ map reveals that most of Earth’s groundwater reserves are stored in tropical and mountain regions, including the Amazon Basin, the Congo, Indonesia, and in North and Central America. Arid regions, as one might presume to be the case, don’t have as much water underground.

“Intuitively, we expect drier areas to have less modern groundwater and more humid areas to have more, but before this study, all we had was intuition,“ said one of the team, Kevin Befus, who is now with the United States Geological Survey. ”Now, we have a quantitative estimate that we compared to geochemical observations.”

The researchers hope their findings, published in Nature Geoscience, will help water managers, policy developers, and scientists to better manage Earth’s remaining groundwater in more sustainable ways. In the meantime, Gleeson will be leading a new study, designed to track depletion rates on a global scale.

“Since we now know how much groundwater is being depleted and how much there is, we will be able to estimate how long until we run out,” he said.

Source: First map of Earth’s hidden groundwater reserves shows we’re using them too quickly

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First map of Earth’s hidden groundwater reserves shows we’re using them too quickly

How the Sun stole Mars’ atmosphere

The solar wind has made Mars a cold desert, and a tougher environment for would-be colonists. Alan Duffy explains the latest research.

 

Four billion years ago, Mars and Earth were like twins. Water flowed on the Martian surface beneath an atmosphere rich in carbon dioxide, oxygen, methane and water vapour. Today the Martian atmosphere is vanishingly thin, just a hundredth the density of Earth’s, and its surface water has disappeared.

Where did it all go? To find out NASA sent MAVEN – the Mars Atmosphere and Volatile Evolution spacecraft – all decked out with sensitive new instruments. It’s been orbiting the planet since last September and this November it finally answered the riddle. The solar wind blew away the Martian atmosphere. This result was the highlight of a landslide of papers published in November using data collected by MAVEN – four inScience and 40 in Geophysical Research Letters.

The first hints water used to flow on Mars came from NASA’s Viking missions in the 1970s. The orbiters beamed back pictures of valleys that looked like they’d been carved by ancient rivers. More recent landers showed fossilised ripples of lakebeds and streams known as mudstone. And just in September, instruments on the Mars Reconnaissance Orbiter detected the signatures of hydrated salts streaking down crater edges. The briny residue showed water may still be found occasionally on the surface of Mars. But it’s a drop in the ocean compared to the bodies of water that resided in the ancient lakes some four billion years ago.

Billions of years ago when the Red Planet was young, it appears to have had a thick atmosphere that was warm enough to support oceans of liquid water – a critical ingredient for life. This animation shows what Mars might have looked like at the time, before transitioning to the dusty red planet we see today.

So where did the water go? Some thought it was locked away in subsurface ice deposits. And as for the atmosphere, carbon dioxide and other gases might have chemically reacted with rocks over hundreds of millions of years, and become locked away inside Mars’ geology – similar to the way carbon dioxide in Earth’s atmosphere can get locked away as limestone.

The other possibility was that both had been lost to space: first the atmosphere, then the water, which in the thin air would simply have evaporated away. If this theory was right, the real question was, why did the atmosphere vanish in the first place? It shouldn’t have: Mars’ gravity, a third of Earth’s, is sufficiently strong to keep its atmosphere.

“Like the theft of a few coins from a cash register every day,

the loss becomes significant over time”

First off, MAVEN established that the Martian atmosphere was indeed vanishing into space. Dipping in and out of the Red Planet’s upper atmosphere, it detected wisps of ionised air escaping at the rate of about 100 grams each second. “Like the theft of a few coins from a cash register every day, the loss becomes significant over time,” says Bruce Jakosky, MAVEN principal investigator at the University of Colorado, Boulder.

MAVEN was also present when a solar storm hit Mars in March 2015.

The rate of atmospheric loss increased up to 20-fold when the storm struck. The storm was the result of a coronal mass ejection by the Sun, which hurled billions of tonnes of superhot material into space. Unlike the constant, steady stream of particles of the solar wind, these events are far more energetic and damaging. With each direct hit, more of the Martian atmosphere is lost.

The Sun had been caught in the act of planetary vandalism. MAVEN’s data showed the long suspected culprit, the solar wind (and its sometime partner in crime, solar storms), was easily capable of removing an atmosphere. While the Sun is still at work shearing away the Martian atmosphere today, four billion years ago a youthful Sun was even more tempestuous with storms that were more frequent and powerful than those of today.

So why was Earth spared this fate? Our planet is blessed with a magnetic shield that deflects the charged solar particles; Mars is not. A magnetic shield is created by a churning liquid iron core, which Earth has. Mars once had a molten core too but around four billion years ago, it cooled and solidified. Just why we have been spared this fate is not entirely understood – perhaps it is simply because Mars is smaller and lost heat more quickly. The same fate undoubtedly awaits Earth too, but not for many millions (if not billions) of years yet.

Without a liquid iron core, Mars’ magnetic field faded away. The solar wind then ripped away most of the atmosphere, leaving the oceans to evaporate into space. But the removal of its atmosphere would have taken place over a few hundred million years, so any life that existed had time to adapt to living underground; the Sun’s ultraviolet radiation would be fatal to life on the surface.

For the first time, NASA’s MAVEN spacecraft has observed the solar winds in action stripping away Mars’ atmosphere. This video shows a simulation of the solar wind striking Mars, then adds a colourful overlay of Mars’ atmosphere being removed (the new measurements taken by MAVEN).

This is good news for scientists hoping to find life on Mars, but bad news for human colonists.

Some had hoped the gases that made up the atmosphere might still be present beneath the surface, awaiting our arrival to unlock all that carbon dioxide, begin to grow plants and terraform the Red Planet. Not so: at least as far as the atmosphere goes, colonisers will need to bring their own.

Source: How the Sun stole Mars’ atmosphere

How the Sun stole Mars’ atmosphere

How Earth looks from outer space

If you were looking with the eye alone, how far away in space would our planet Earth still be visible?

Here is Earth from 900 million miles away, from the vantage point of the rings of Saturn.  Image via the Cassini spacecraft, which has been orbiting Saturn since 2004.

How far away from Earth can we be, to see it still with our own eyes?

To answer this question, you have to take into account how brightly Earth reflects sunlight. And the sun itself is an important factor. As seen from any great distance, Earth appears right next to the sun – and, from a great distance, the glare of our local star would make Earth difficult or impossible to see. But spacecraft exploring our solar system have given us marvelous views of Earth. So imagine blasting off and being about 300 kilometers – about 200 miles – above Earth’s surface. That’s the height at which the International Space Station (ISS) orbits. The surface of the Earth looms large in the window of ISS. In the daytime, you can clearly see major landforms. At night, you see the lights of Earth’s cities.

Earth in daylight, from ISS in 2012. The U.S. Great Lakes shine in the sun.  Read more about this image.

ng at an altitude of about 240 miles over the eastern North Atlantic, the Expedition 30 crew aboard the International Space Station photographed this nighttime scene. This view looks northeastward. Center point coordinates are 46.8 degrees north latitude and 14.3 degrees west longitude. The night lights of the cities of Ireland, in the foreground, and the United Kingdom, in the back and to the right, are contrasted by the bright sunrise in the background. The greens and purples of the Aurora Borealis are seen along the rest of the horizon. This image was taken on March 28, 2012.

As you pass the moon – about 380,000 kilometers away – or a quarter million miles – Earth looks like a bright ball in space – not very different from the way the moon looks to us. The first images of the Earth from the moon came from the Apollo mission. Apollo 8 in 1968 was the first human spaceflight to leave Earth orbit. It was the first earthly spacecraft to be captured by and escape from the gravitational field of another celestial body, in this case the moon. It was the first voyage in which humans visited another world and returned to return to Earth.

Then came the mind-blowing moment of seeing both the Earth and moon together in space. The next picture shows a crescent-shaped Earth and moon – the first of its kind ever taken by a spacecraft – on September 18, 1977. NASA’s Voyager 1 spacecraft was 7.25 million miles (11.66 million kilometers) from Earth at the time.

Now moon exploration has become more common, though still amazing. This mosaic below shows images of Earth and the moon acquired by the multispectral imager on the Near Earth Asteroid Rendezvous Spacecraft (NEAR) on January 23, 1998, 19 hours after the spacecraft swung by Earth on its way to the asteroid 433 Eros. The images of both were taken from a range of 250,000 miles (400,000 kilometers), approximately the same as the distance between the two bodies.

This mosaic shows images of Earth and the moon acquired by the multispectral imager on the Near Earth Asteroid Rendezvous Spacecraft (NEAR) on January 23, 1998, 19 hours after the spacecraft swung by Earth on its way to the asteroid 433 Eros. The images of both were taken from a range of 250,000 miles (400,000 kilometers), approximately the same as the distance between the two bodies.  Read more about this image.

The robotic Kaguya spacecraft orbited around Earth’s moon in 2007. Launched by Jpan, and officially named the Selenological and Engineering Explorer (SELENE), studied the origin and evolution of the moon. The frame below is from Kaguya’s onboard HDTV camera.

The robotic Kaguya spacecraft orbited around Earth's moon in 2007. Japan launched this scientific mission of the Selenological and Engineering Explorer (SELENE), nicknamed Kaguya, in order to study the origin and evolution of the moon. This frame is from Kaguya's onboard HDTV camera.

Another image from ___, which captured the Japanese craft got footage and stills of Earth setting.  Remember that, if you were on the moon, you would not see Earth rise or set.  But spacecraft in orbit around the moon do experience this scene.

Speeding outward from the Earth and moon system, you pass the orbits of the planets Mars, Jupiter, Saturn, Uranus and Neptune. From all of these worlds, Earth looks like a star – which gets fainter as you get farther away. From the world next door, though, Mars, a human observer with normal vision could easily see Earth and the moon as two distinct, bright evening or morning “stars.”

Earth and moon, as seen from Mars by the Curiosity rover on January 31, 2014.  Read more about this image.

This is the famous image known as Pale Blue Dot.  It's a photograph of Earth taken on February 14, 1990, by the Voyager 1 space probe from a record distance of about 6 billion kilometers (3.7 billion miles).

The light from Earth finally becomes too faint to see with the eye alone at around 14 billion kilometers – about 9 billion miles – from home – around the outer limit of our solar system – nowhere near as far as even the next-nearest star. Of course, if an astronaut or alien had a telescope, he or she could definitely see Earth further away than that.

Bottom line: How far away in space can you view Earth with the eye alone? About as far away as the outer reaches of our own solar system at about 14 billion kilometers – about 9 billion miles – from home.

Source: How Earth looks from outer space

How Earth looks from outer space

EarthSky’s meteor shower guide for 2015

The Delta Aquarid meteor shower – which always happens in late July and early August – is going on now, but bright moonlight is interfering. Click here for more about the Delta Aquarids. This shower overlaps with the famous Perseid meteor shower, which will peak on the mornings of August 11, 12 and 13. It’s going to be a wonderful year for the Perseids! The moon is out of the way. Click here for more about the Perseids. And follow the links below to learn what to expect for meteor showers during the rest of 2015.

January 3-4, 2015 Quadrantids

April 22-23, 2015 Lyrids

May 5-6, 2015 Eta Aquarids

July 28-29, 2015 Delta Aquarids

August 12-13, 2015 Perseids

October 8, 2015 Draconids

October 21-22, 2015 Orionids

November 4-5, 2015 South Taurids

November 12-13, 2015 North Taurids

November 17-18, 2015 Leonids

December 13-14, 2015 Geminids

A word about moonlight

Most important: a dark sky

Know your dates and times

Where to go to watch a meteor shower

What to bring with you

Are the predictions reliable?

Remember …

View larger. | Scott MacNeill created this wonderful composite image at Frosty Drew Observatory in Charlestown, Rhode Island, USA.  We love this image, because you can see the meteors coming from their radiant point in the constellation Perseus.  Thank you, Scott!

January 4, 2015 before dawn, the Quadrantids

Although the Quadrantids can produce over 100 meteors per hour, the sharp peak of this shower tends to last only a few hours, and doesn’t always come at an opportune time. In other words, you have to be in the right spot on Earth to view this meteor shower in all its splendor. The radiant point is in the part of the sky that used to be considered the constellation Quadrans Muralis the Mural Quadrant. You’ll find this radiant near the famous Big Dipper asterism (chart here), in the north-northeastern sky after midnight and highest up before dawn. Because the radiant is fairly far to the north on the sky’s dome, meteor numbers will be greater in the Northern Hemisphere. In 2015, watch in the wee hours – after midnight and before dawn – on January 4. Unfortunately, the almost-fullwaxing gibbous moon is out almost all night long, sitting low in the west in the dark hour before dawn.Click here to find out your moonset time..

Everything you need to know: Quadrantid meteor shower

Around the March equinox … fireball season. A fireball is just an especially bright meteor. Northern spring and southern autumn – for a few weeks around the March equinox – is a good time to see one. It’s fireball season — a time of year when bright meteors appear in greater numbers than usual. In fact, in the weeks around the equinox, the appearance rate of fireballs can increase by as much as 30 percent, says NASA.

April 22 and 23, 2015 before dawn, the Lyrids
The Lyrid meteor shower – April’s shooting stars – lasts from about April 16 to 25. Lyrid meteors tend to be bright and often leave trails. About 10-20 meteors per hour can be expected at their peak. Plus, the Lyrids are known for uncommon surges that can sometimes bring the rate up to 100 per hour. Those rare outbursts are not easy to predict, but they’re one of the reasons the tantalizing Lyrids are worth checking out around their peak morning. The radiant for this shower is near the bright star Vega in the constellation Lyra (chart here), which rises in the northeast at about 10 p.m. on April evenings.In 2015, the peak morning is April 23. Watch also on the morning of April 22. And you might also see Lyrid meteors before and after that date. The waxing crescent moon will set in the evening, leaving a dark for watching this year’s Lyrid shower.

Everything you need to know: Lyrid meteor shower

May 6, 2015 before dawn, the Eta Aquarids
This meteor shower has a relatively broad maximum – meaning you can watch it for several days around the predicted peak. However, in 2015, the bright waning gibbous moon is sure to diminish the numbers. The radiant is near the star Eta in the constellation Aquarius the Water Bearer (click here for chart). The radiant comes over the eastern horizon at about 4 a.m. local time; that is the time at all locations across the globe. For that reason, the hour or two before dawn tends to offer the most Eta Aquarid meteors, no matter where you are on Earth. At northerly latitudes – like those in the northern U.S. and Canada, or northern Europe, for example – the meteor numbers are typically lower for this shower. In the southern half of the U.S., 10 to 20 meteors per hour might be visible in a dark sky. Farther south – for example, at latitudes in the Southern Hemisphere – the meteor numbers may increase dramatically, with perhaps two to three times more Eta Aquarid meteors streaking the southern skies. For the most part, the Eta Aquarids is a predawn shower. In 2015, the bright waning gibbous moon will obscure this year’s production. The most meteors will probably rain down on May 6, in the dark hours before dawn. But watch on May 5 and 7 as well! The broad peak to this shower means that some meteors may fly in the dark hour before dawn for a few days before and after the predicted optimal date.

Everything you need to know: Eta Aquarid meteor shower

Late July and early August, 2015, the Delta Aquarids
Like the Eta Aquarids in May, the Delta Aquarid meteor shower in July favors the Southern Hemisphere and tropical latitudes in the Northern Hemisphere. The meteors appear to radiate from near the star Skat or Delta in the constellation Aquarius the Water Bearer. The maximum hourly rate can reach 15-20 meteors in a dark sky. The nominal peak is around July 27-30, but, unlike many meteor showers, the Delta Aquarids lack a very definite peak. Instead, these medium-speed meteors ramble along fairly steadily throughout late July and early August. An hour or two before dawn usually presents the most favorable view of the Delta Aquarids. At the shower’s peak in late July, 2015, the rather faint Delta Aquarid meteors will have to contend with moonlight. The waxing gibbous moon will be out until the wee hours after midnight. Try watching in late July predawn sky, after moonset.

Everything you need to know: Delta Aquarid shower

August 12-13, 2015 before dawn, the Perseids
The Perseid meteor shower is perhaps the most beloved meteor shower of the year for the Northern Hemisphere. Fortunately, the slender waning crescent moon rising at or near dawn will not obtrude on this year’s shower. The Perseid shower builds gradually to a peak, often produces 50 to 100 meteors per hour in a dark sky at the peak, and, for us in the Northern Hemisphere, this shower comes when the weather is warm. The Perseids tend to strengthen in number as late night deepens into midnight, and typically produce the most meteors in the wee hours before dawn. They radiate from a point in the constellation Perseus the Hero, but, as with all meteor shower radiant points, you don’t need to know Perseus to watch the shower; instead, the meteors appear in all parts of the sky. They are typically fast and bright meteors. They frequently leave persistent trains. Every year, you can look for the Perseids to peak around August 10-13. Predicted peak mornings in 2015: August 11, 12 and 13. The Perseids combine with the Delta Aquarid shower (above) to produce a dazzling display of shooting stars on what are, for us in the N. Hemisphere, warm summer nights. In 2015, as always, the Perseid meteors will be building to a peak from early August until the peak nights; afterwards, they drop off fairly rapidly. With little or no moon to ruin the show, this is a great year for watching the Perseid meteor shower.

Everything you need to know: Perseid meteor shower

October 8, 2015, the Draconids
The radiant point for the Draconid meteor shower almost coincides with the head of the constellation Draco the Dragon in the northern sky. That’s why the Draconids are best viewed from the Northern Hemisphere. The Draconid shower is a real oddity, in that the radiant point stands highest in the sky as darkness falls. That means that, unlike many meteor showers, more Draconids are likely to fly in the evening hours than in the morning hours after midnight. This shower is usually a sleeper, producing only a handful of languid meteors per hour in most years. But watch out if the Dragon awakes! In rare instances, fiery Draco has been known to spew forth many hundreds of meteors in a single hour. In 2015, the waning crescent moon rises at late night and will not intrude on this year’s Draconid shower. Try watching at nightfall and early evening on October 8 and 9.

Everything you need to know: Draconid Meteor shower

October 22, 2015 before dawn, the Orionids
On a dark, moonless night, the Orionids exhibit a maximum of about 10 to 20 meteors per hour. The waxing gibbous moon will be out the during the evening hours, but it’ll set before the prime time viewing hours, providing deliciously dark skies for this year’s Orionid shower. More meteors tend to fly after midnight, and the Orionids are typically at their best in the wee hours before dawn. These fast-moving meteors occasionally leave persistent trains. They sometimes produce bright fireballs, so watch for them to flame in the sky. If you trace these meteors backward, they seem to come from the Club of the famous constellation Orion the Hunter. You might know Orion’s bright, ruddy star Betelgeuse. The radiant is north of Betelgeuse. The Orionids have a broad and irregular peak that isn’t easy to predict. This year, 2015, presents a fine year for watching the Orionid meteor shower. The best viewing for the Orionids in 2015 will probably be before dawn on October 22. Try the days before and after that, too, sticking to the midnight-to-dawn hours..

Everything you need to know: Orionid meteor shower

Late night November 4 until dawn November 5, 2015, the South Taurids
Fortunately, the full moon will wash away all but the brightest South Taurid meteors. The meteoroid streams that feed the South (and North) Taurids are very spread out and diffuse. That means the Taurids are extremely long-lasting (September 25 to November 25) but usually don’t offer more than about 7 meteors per hour. That is true even on the South Taurids’ expected peak night. The Taurids are, however, well known for having a high percentage of fireballs, or exceptionally bright meteors. Plus, the other Taurid shower – the North Taurids – always adds a few more meteors to the mix during the South Taurids’ peak night. In 2015, the slim waning crescent moon coming up before dawn will not seriously obtrude on this year’s South Taurid meteor shower. The South Taurids should produce their greatest number of meteors in the wee hours – between midnight and dawn – on November 5. Remember, it’ll be possible to catch a fireball or two!

Late night November 12 until dawn November 13, 2015, the North Taurids
Like the South Taurids, the North Taurids meteor shower is long-lasting (October 12 – December 2) but modest, and the peak number is forecast at about 7 meteors per hour. The North and South Taurids combine, however, to provide a nice sprinkling of meteors throughout October and November. Typically, you see the maximum numbers at around midnight, when Taurus the Bull is highest in the sky. Taurid meteors tend to be slow-moving, but sometimes very bright. In 2015, the new moon comes only one day before the predicted peak, providing a dark sky for the 2015 North Taurid shower.

Late night November 17 until dawn November 18, 2015, the Leonids
Radiating from the constellation Leo the Lion, the famous Leonid meteor shower has produced some of the greatest meteor storms in history – at least one in living memory, 1966 – with rates as high as thousands of meteors per minute during a span of 15 minutes on the morning of November 17, 1966. Indeed, on that beautiful night in 1966, the meteors did, briefly, fall like rain. Some who witnessed the 1966 Leonid meteor storm said they felt as if they needed to grip the ground, so strong was the impression of Earth plowing along through space, fording the meteoroid stream. The meteors, after all, were all streaming from a single point in the sky – the radiant point – in this case in the constellation Leo the Lion. Leonid meteor storms sometimes recur in cycles of 33 to 34 years, but the Leonids around the turn of the century – while wonderful for many observers – did not match the shower of 1966. And, in most years, the Lion whimpers rather than roars, producing a maximum of perhaps 10-15 meteors per hour on a dark night. Like many meteor showers, the Leonids ordinarily pick up steam after midnight and display the greatest meteor numbers just before dawn. In 2015, the rather wide waxing crescent moon sets in the evening and won’t interfere with this year’s Leonid meteor shower. The peak morning will probably be November 18 – but try November 17, too.

Everything you need to know: Leonid meteor shower

December 13-14, 2015, mid-evening until dawn, Geminids
Radiating from near the bright stars Castor and Pollux in the constellation Gemini the Twins, the Geminid meteor shower is one of the finest meteors showers visible in either the Northern or the Southern Hemisphere. Best yet, there is no moon to obscure the 2015 Geminid shower. The meteors are plentiful, rivaling the August Perseids, with perhaps 50 to 100 meteors per hour visible at the peak. Plus Geminid meteors are often bright. These meteors are often about as good in the evening as in the hours between midnight and dawn. In 2015, the slender waxing crescent moon will set soon after the sun, providing a wonderful cover of darkness for the Geminid meteor shower. Your best bet is to watch on December 12-13 and 13-14, from mid-evening (9 to 10 p.m.) until dawn.

Animation Credit: NASA MSFC

A word about moonlight. In 2015, moonlight will not pose much of a problem for the April Lyrids, August Perseids, October Draconids, October Orionids, November South Taurids, November North Taurids, November Leonids and December Geminids. There’s some moon-free viewing time for the July Delta Aquarids. The nearly full moon gets in the way of the January Quadrantids and May Eta Aquarids. Our almanac page provides links for access to the moonrise and moonset times in your sky.

Most important: a dark sky. Here’s the first thing – the main thing – you need to know to become as proficient as the experts at watching meteors. That is, to watch meteors, you need a dark sky. It’s possible to catch a meteor or two or even more from the suburbs. But, to experience a true meteor shower – where you might see several meteor each minute – avoid city lights.

Know your dates and times. You also need to be looking on the right date, at the right time of night. Meteor showers occur over a range of dates, because they stem from Earth’s own movement through space. As we orbit the sun, we cross “meteor streams.” These streams of icy particles in space come from comets moving in orbit around the sun. Comets are fragile icy bodies that litter their orbits with debris. When this cometary debris enters our atmosphere, it vaporizes due to friction with the air. If moonlight or city lights don’t obscure the view, we on Earth see the falling, vaporizing particles as meteors. The Lyrids take place between about April 16 and 25. The peak morning in 2015 should be April 22, but you might catch Lyrid meteors on the nights around that date as well.

Where to go to watch a meteor shower. You can comfortably watch meteors from many places, assuming you have a dark sky: a rural back yard or deck, the hood of your car, the side of a road. State parks and national parks are good bets, but be sure they have a wide open viewing area, like a field; you don’t want to be stuck in the midst of a forest on meteor night. An EarthSky friend and veteran meteor-watcher and astrophotographer Sergio Garcia Rill also offers this specific advice:

… you might want to give it a try but don’t know where to go. Well, in planning my night photoshoots I use a variety of apps and web pages to know how dark the sky is in a certain location, the weather forecast, and how the night sky will look. Here’s the link toDark Sky Finder. It’s a website that shows the light pollution in and around cities in North America which has been fundamental for finding dark sites to setup shots. Dark Sky finder also has an app for iPhone and iPad which as of this writting is only 99 cents so you might want to look into that as well. For people not in North America, the Blue Marble Navigator might be able to help to see how bright are the lights near you.

The other tool I can suggest is the Clear Sky Chart. I’ve learned the hard way that, now matter how perfectly dark the sky is at your location, it won’t matter if there’s a layer of clouds between you an the stars. This page is a little hard to read, but it shows a time chart, with each column being an hour, and each row being one of the conditions like cloud coverage and darkness. Alternatively, you could try to see the regular weather forecast at the weather channel or your favorite weather app.

What to bring with you. You don’t need special equipment to watch a meteor shower. If you want to bring along equipment to make yourself more comfortable, consider a blanket or reclining lawn chair, a thermos with a hot drink, binoculars for gazing at the stars. Be sure to dress warmly enough, even in spring or summer, especially in the hours before dawn. Binoculars are fun to have, too. You won’t need them for watching the meteor shower, but, especially if you have a dark sky, you might not be able to resist pointing them at the starry sky.

Are the predictions reliable? Although astronomers have tried to publish exact predictions in recent years, meteor showers remain notoriously unpredictable. Your best bet is to go outside at the times we suggest, and plan to spend at least an hour, if not a whole night, reclining comfortably while looking up at the sky. Also remember that meteor showers typically don’t just happen on one night. They span a range of dates. So the morning before or after a shower’s peak might be good, too.

Remember … meteor showers are like fishing. You go, you enjoy nature … and sometimes you catch something.

Peak dates are derived from data published in the Observer’s Handbook by the Royal Astronomical Society of Canada and Guy Ottewell’s Astronomical Calendar.

Dick Dionne in Green Valley, Arizona caught this bright Taurid fireball on November 15, 2014.  Many reported fireballs in early November this year!

EarthSky Facebook friend Eddie Popovits caught this Perseid fireball in early August 2014.

Eta Aquarid meteor captured on May 6, 2014 by Mike Taylor.  Visit Taylor Photography.

View larger. | Simon Waldram in the Canary Islands caught this Lyrid meteor on the night of April 20-21, 2014.  Thank you, Simon!

Mike O'Neal posted this on the EarthSky Facebook page today (April 22).  He wrote, 'Had mostly cloudy sky, but did see some beautiful ones between the breaks.'

A North Taurid meteor seen fleeing its radiant point near the Pleiades in the constellation Taurus.  Captured by EarthSky Facebook friend Abhijit Juvekar on November 12, 2013.  Thank you, Abhijit!

View larger. | Scott MacNeill created this wonderful composite image at Frosty Drew Observatory in Charlestown, Rhode Island, USA.  We love this image, because you can see the meteors coming from their radiant point in the constellation Perseus.  Thank you, Scott!

Eta Aquarid meteor seen by EarthSky Facebook friend Ann Dinsmore on the morning of May 5, 2013.  View larger.  Thanks Ann!

From EarthSky Facebook friend Guy Livesay. He wrote, ' Didn't see many Lyrids on the 21st or 22nd in Eastern NC. This is from the 21st. There's actually 2 in this shot very close together.'

Bottom line: The Lyrid meteor shower is next on the mornings of April 22 and 23. April 23 will probably have more meteors. Details on how to watch, plus listings of all major meteor showers in 2015.

EarthSky’s top 10 tips for meteor-watchers

 Source:  EarthSky’s meteor shower guide for 2015

EarthSky’s meteor shower guide for 2015

Why we live on Earth and not Venus

Compared to its celestial neighbours Venus and Mars, Earth is a pretty habitable place. So how did we get so lucky? A new study sheds light on the improbable evolutionary path that enabled Earth to sustain life.

The research, published this week in Nature Geoscience, suggests that Earth’s first crust, which was rich in radioactive heat-producing elements such as uranium and potassium, was torn from the planet and lost to space when asteroids bombarded the planet early in its history. This phenomenon, known as impact erosion, helps explain a landmark discovery made over a decade ago about the Earth’s composition.

Researchers with the University of British Columbia and University of California, Santa Barbara say that the early loss of these two elements ultimately determined the evolution of Earth’s plate tectonics, magnetic field and climate.

“The events that define the early formation and bulk composition of Earth govern, in part, the subsequent tectonic, magnetic and climatic histories of our planet, all of which have to work together to create the Earth in which we live,” said Mark Jellinek, a professor in the Department of Earth, Ocean & Atmospheric Sciences at UBC. “It’s these events that potentially differentiate Earth from other planets.”

On Earth, shifting tectonic plates cause regular overturning of Earth’s surface, which steadily cools the underlying mantle, maintains the planet’s strong magnetic field and stimulates volcanic activity. Erupting volcanoes release greenhouse gases from deep inside the planet and regular eruptions help to maintain the habitable climate that distinguishes Earth from all other rocky planets.

Venus is the most similar planet to Earth in terms of size, mass, density, gravity and composition. While Earth has had a stable and habitable climate over geological time, Venus is in a climate catastrophe with a thick carbon dioxide atmosphere and surface temperatures reaching about 470 C. In this study, Jellinek and Matt Jackson, an associate professor at the University of California, explain why the two planets could have evolved so differently.

“Earth could have easily ended up like present day Venus,” said Jellinek. “A key difference that can tip the balance, however, may be differing extents of impact erosion.”

With less impact erosion, Venus would cool episodically with catastrophic swings in the intensity of volcanic activity driving dramatic and billion-year-long swings in climate.

“We played out this impact erosion story forward in time and we were able to show that the effect of the conditions governing the initial composition of a planet can have profound consequences for its evolution. It’s a very special set of circumstances that make Earth.”

Story Source:

The above post is reprinted from materials provided by University of British ColumbiaNote: Materials may be edited for content and length.


Journal Reference:

  1. A. M. Jellinek, M. G. Jackson. Connections between the bulk composition, geodynamics and habitability of EarthNature Geoscience, 2015; DOI: 10.1038/ngeo2488
Why we live on Earth and not Venus

Space Silicon Valley Titan Yuri Milner Bets $100M On Finding Alien Life

The Lick Observatory’s Automated Planet Finder Will Help Out In The Search For Life

For more than a decade, the giant satellite dishes of the Allen Telescope Array have been trained on the skies, attempting to eavesdrop on alien conversations. Named after Microsoft co-founder Paul Allen, the 42 dish antennae at the SETI Institute in California have been mankind’s greatest attempt to search for intelligent life in the cosmos. Unfortunately, any ETs out there have been radio silent so far, and funding for SETI (Search for Extraterrestrial Intelligence) has dried up over time.

Now the hunt for alien life is getting reinvigorated, thanks to a huge investment from Silicon Valley’s Yuri Milner. The Russian billionaire has been supporting research in physics, mathematics and the life sciences through the Breakthrough Prize, which is the largest scientific award in the world, and now he’s investing $100 million to complete the most extensive search for life beyond Earth to date. The project, called Breakthrough Listen, is endorsed by physicist Stephen Hawking and led by SETI pioneer Frank Drake as well as other top-notch scientists.

“We believe that life arose spontaneously on Earth,” said Hawking in a press conference. “So, in an infinite universe, there must be other occurrences of life… We are alive, we are intelligent, we must know.”

The Breakthrough Listen project “gives us the opportunity to do something unprecedented,” says Geoff Marcy, who has discovered dozens of alien planets and will now search for aliens as one of the leaders of the Breakthrough Listen project. He’s an astronomer at the University of California at Berkeley. “We plan to do the deepest, most complete survey of radio transmissions from extraterrestrial life.”

How It Works

The Parkes Observatory

Located in Australia, this 210-foot telescope will scan for extraterrestrial radio waves for the Breakthrough Listen project.

Over the next ten years, Breakthrough Listen will scan the 1 million closest stars to Earth, as well as the center of our galaxy and the 100 nearest neighboring galaxies, for hints of intelligent transmissions. The number of targets is 10 times higher than any other program. It will also scan 5 times more radio frequencies and do it all 100 times faster than ever before.

“The idea is to bring a Silicon Valley approach to the search for life,” said Milner. “That is, an approach to data that is transparent, that is innovative, and that uses the power of crowdsourcing.”

For this extensive search the team use two large radio telescopes: the Green Bank Telescope in West Virginia, and the Parkes Observatory in Australia. Together, the two telescopes provide coverage of the northern and southern hemispheres. And with new equipment that’s under development at UC Berkeley, the project will be able to scan and process radio signals across 1.5 billion frequencies simultaneously.

“This would be like tuning your radio dial, and instead of hearing the broadcast from one radio station, we’re going to be listening to 1.5 billion channels,” says Marcy. By contrast, the SETI Institute is able to scan four frequency bands at a time. “This is a huge technological leap,” says Marcy. “Nobody can do this now, but the team at UC Berkeley is going to build from scratch a set of modules that will survey 1.5 billion frequencies.”

In those frequencies, the modules will also look for patterns that might signal intelligent life.

Why Now?

Just in the past few years, astronomers have been learning that Earth may not be as unique as it seems. There are billions of planets in the Milky Way, and according tocalculations by Geoff Marcy’s team, about a quarter of the Sun-like stars in our galaxy are home to Earth-like planets that are not too hot and not too cold to have liquid water. That means, theoretically, plenty of chances for life to flourish, and some of those lifeforms may have evolved enough intelligence to communicate with radio waves.

Can You Hear Me Now?

With its 328-foot dish, the Green Banks Telescope in West Virginia is the world’s largest steerable radio telescope. It can scan 80 percent of the sky for radio transmissions.

Also fortuitous for the project was the fact that two large radio telescopes became open to outside investments. The Green Bank Telescope wasn’t earning enough money to support itself, despite funding from the National Science Foundation. The telescope might have been shut down if it hadn’t been for the Breakthrough investment. The Parkes telescope, too, wasfacing budget cuts. Going forward, the two telescopes will each dedicate 15 percent of their time to searching for radio transmissions from intelligent extraterrestrials.

The third impetus is the rapid advancement of technology. “Digital high-bandwidth technology is improving very quickly,” says Marcy. “We now have computing tech that makes it possible to scan large numbers of frequencies much larger than has ever been processed before.”

If a civilization near one of the 1,000 nearest stars to Earth transmits a radio signal with the power of an aircraft radar, Breakthrough Listen says it will be able to hear it. But the further away the star system, the stronger the signal needs to be in order for Earth-based telescopes to detect it. For example, at the center of the Milky Way, the signal would need to be at least a dozen times stronger than the interplanetary radar we use to probe our solar system.

Frickin’ Laser Beams

Breakthrough Listen will do more than listen for alien radio transmissions—it will also look for laser pulses. The team will use the Automated Planet Finder Telescope in California to search for optical signals that advanced civilizations may use to communicate.

“One really good way to communicate across the light-years of distances between stars is to use lasers,” says Marcy. “They’re very bright, the beam is very confined, and the light is at just one frequency so the other party can tune in to that frequency. We might wonder, does our Milky Way galaxy have some kind of galactic Internet to communicate between planetary systems and spacecraft? It can’t be done with wires or fiber optics. It could be done, however, with laser beams.”

“Is the Earth the lone harborer of intelligent sentient creatures in all the depths of the cosmos?”

The project’s optical search is sensitive enough to detect a 100 watt laser (that’s about as bright as a light bulb in your house) from 25 trillion miles away.

What Will They Find?

“Breakthrough Listen is an absolutely historic opportunity to make progress toward answering a question that has been with humanity since time immemorial: Is the Earth the lone harborer of intelligent sentient creatures in all the depths of the cosmos?” says astrophysicist and alien hunter Andrew Siemion, another of the project’s leaders.

Will the project find what it’s looking for? The scientists involved say it’s a long-shot, but we won’t know until we try.

“They might be there, they might not,” says Hawking. “But recent experiments like the Kepler mission have changed the game. We now know there are so many worlds, and organic molecules are so common, that it seems quite likely that life is out there, but intelligence is a great unknown. It only took 500 million years for life to evolve on earth, but it took 2.5 billion years to get from the earliest cells to multi-cell animals, and technological intelligence has appeared only once, so it may be very rare. And when it does evolve, we only need to look in the mirror to know that it can be fragile and prone to self-destruction.”

If intelligent civilizations are out there, we don’t know if they’re 10 light-years away or 10 million, says Marcy. It would take a signal from the latter civilization 10 million years to reach us. Plus, there are so many stars and so many channels that could be used for communication that astronomer Jill Tarter once compared the search for extraterrestrial intelligence to dipping a glass in the ocean to look for fish. At least the glass is getting bigger, though.

Siemion thinks there is a small but reasonable chance that the project will pick up on alien signals in the next 5 to 10 years. “This will be an incredible achievement, and will either result in the detection of advanced life elsewhere in the universe or will tell us that humanity is even more rare and unique than we imagine.”

“Does our Milky Way galaxy have some kind of galactic Internet to communicate between planetary systems and spacecraft?”

If the search comes up empty, Marcy says, “the next generation is going to have to do better. They’ll need to use larger telescopes that are more sensitive and reach down to radio flux levels that are even fainter.”

Such telescopes are already on the horizon—including the Square Kilometer Array being built in Australia. When it comes online in 2020, it will be 50 times more sensitive than any other radio telescope.

You Can Participate, Too

Breakthrough Listen will generate more data in a year than any other previous search. All of it will be publicly available so anyone with an alien-hunting penchant can peruse it and find new ways to analyze it. The frequency-scanning software under development will be open-source as well, so that other telescopes can lend a hand to the search for life. And you can too, by donating your computer’s down-time to analyzing data throughSETI@home.

Milner’s group is also offering up to $1 million in prizes in a competition to compose a message that “represents humanity, and represents our little speck of dust, the planet Earth,” says Marcy. “We’re asking people to submit a message that they think best captures the essence of our lives, our species, our hopes and dreams, and our nature. That will be a challenge.”

The group has no intention of broadcasting such a message into outer space, out of fear of attracting potentially hostile alien civilizations. Rather, “We hope to encourage people to think about humanity as a rather fragile species living on a small, fragile planet,” says Marcy, “and that our greatest calling is to take care of our planet, and to take care of ourselves.”

Source: Space Silicon Valley Titan Yuri Milner Bets $100M On Finding Alien Life

Space Silicon Valley Titan Yuri Milner Bets $100M On Finding Alien Life