Category: Space & Physics

Does It Snow on Mars?

By David Rothery, The Open University | August 22, 2017 10:08 am
mars-snow

What Mars could have looked like during an ice age 400,000 years ago. (Credit: NASA/JPL)

Given that there are ambitious plans to colonize Mars in the near future, it is surprising how much we still have to learn about what it would be like to actually live on the planet. Take the weather, for instance. We know there are wild fluctuations in Mars’s climate – and that it is very windy and at times cloudy (though too cold and dry for rainfall). But does it snow? Might settlers on Mars be able to see the red planet turn white? A new study surprisingly suggests so.

Mars is clearly cold enough for snow. It has ice – the amount of which has varied significantly over time. When its axis is tilted at only a small angle relative to its orbit, its surface is ice-free except for the polar caps. This is the situation today, when its axial tilt is 25⁰ (similar to Earth’s 23⁰ axial tilt). However, possibly because Mars lacks a large moon to stabilize its spin, there have been times when its spin axis was tipped over by up to 60⁰ – allowing the polar ice caps to spread, maybe even to the extent that there was abundant ice near the equator.

NASA’s Phoenix Mars Lander didn’t see snow on the ground. (Credit: NASA/JPL-Caltech/University of Arizona/Texas A&M University)

Mars emerged from its most recent ice age about 400,000 years ago. Since then, its polar caps have been small, and any ice surviving near the equator has been buried under dust.

The planet’s atmosphere is of low pressure and very dry. Although it is still possible for clouds to form at an altitude of several kilometers, until now it has been generally believed that any true snowfall would not reach the ground. The clouds, resembling Earth’s cirrus clouds, are believed to form when the small amount of water vapor in the atmosphere condenses (directly from vapor to ice) onto grains of dust lofted skywards during storms.

Winter Wonderland?

Being only a few micrometers in size, ice particles falling from the clouds would would drop at about only a centimeter a second. This allows more than enough time for them to evaporate before reaching the ground (strictly speaking, the process should be called “sublimation”, because the ice goes directly to vapor, without melting first). Overnight and seasonal frost spotted on Mars have been explained by water-ice particles falling quickly because they had been made temporarily larger and heavier by an outer coating of frozen carbon dioxide from the atmosphere.

Seasonal frost (or snowfall?) in gullies on a crater wall on Mars, at 60⁰ N. This view is about 800 metres wide. (Credit: NASA/JPL/University of Arizona)

The new study, published in Nature Geoscience, has found a way in which tiny specks of water-ice could travel down to the ground without this strange frozen carbon dioxide coat. If correct, this would mean genuine snow on Mars – just like that on Earth. The team used measurements from two orbiting spacecraft (the Mars Global Surveyor and Mars Reconnaissance Orbiter) to study how temperature varies with height in the Martian atmosphere. They found that at night, the lower atmosphere below ice clouds can become unstable, because it becomes less dense below than above.

This leads to rapid downdrafts of air, traveling at about 10 meters per second, which could carry ice crystals to the surface too quickly for them to “evaporate”. However, the snow layer would probably be thin and not last too long before it sublimes back into the atmosphere – where it could form new clouds and snowfall.

The phenomenon is similar to what is known on Earth a “microburst”, when a localized 60mph (97km per hour) downdraft below a thunderstorm can be powerful enough to flatten trees. The same process can also be responsible for intense snowfall at a particular location, by carrying snowflakes groundward in a blast, punching through the near-surface layer of air that would normally be warm enough to melt them.


A microburst on Earth.

Snow has not yet been observed in the process of actually reaching the ground on Mars, but it has been seen falling through the sky. NASA’s Phoenix lander, which landed at 68⁰ N in 2008 and became famous for finding ice below the surface when it scraped the dirt away, studied the sky above too. It used a LIDAR (like radar but relying on reflections from a laser beam) to probe the atmosphere, and on at least two nights observed curtains of falling snow hanging below the cloud layer.

Frost or a light dusting of snow seen at the Viking 2 lander site, Utopia Planitia, Mars. (Credit: Vandencbulek Eric, CC BY)

The ConversationIf a downdraft powerful enough had occurred, then maybe one morning Phoenix would have woken up to a winter wonderland, instead of the usual red landscape – at least for a few hours.

 

This article was originally published on The Conversation. Read the original article.

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MORE ABOUT: Mars

Creating a Universe in the Lab? The Idea Is No Joke

By Zeeya Merali | June 19, 2017 1:15 pm
universe

(Credit: Shutterstock)

Physicists aren’t often reprimanded for using risqué humor in their academic writings, but in 1991 that is exactly what happened to the cosmologist Andrei Linde at Stanford University. He had submitted a draft article entitled ‘Hard Art of the Universe Creation’ to the journal Nuclear Physics B. In it, he outlined the possibility of creating a universe in a laboratory: a whole new cosmos that might one day evolve its own stars, planets and intelligent life. Near the end, Linde made a seemingly flippant suggestion that our Universe itself might have been knocked together by an alien ‘physicist hacker’. The paper’s referees objected to this ‘dirty joke’; religious people might be offended that scientists were aiming to steal the feat of universe-making out of the hands of God, they worried. Linde changed the paper’s title and abstract but held firm over the line that our Universe could have been made by an alien scientist. ‘I am not so sure that this is just a joke,’ he told me.

Fast-forward a quarter of a century, and the notion of universe-making – or ‘cosmogenesis’ as I dub it – seems less comical than ever. I’ve travelled the world talking to physicists who take the concept seriously, and who have even sketched out rough blueprints for how humanity might one day achieve it. Linde’s referees might have been right to be concerned, but they were asking the wrong questions. The issue is not who might be offended by cosmogenesis, but what would happen if it were truly possible. How would we handle the theological implications? What moral responsibilities would come with fallible humans taking on the role of cosmic creators?

Theoretical physicists have grappled for years with related questions as part of their considerations of how our own Universe began. In the 1980s, the cosmologist Alex Vilenkin at Tufts University in Massachusetts came up with a mechanism through which the laws of quantum mechanics could have generated an inflating universe from a state in which there was no time, no space and no matter. There’s an established principle in quantum theory that pairs of particles can spontaneously, momentarily pop out of empty space. Vilenkin took this notion a step further, arguing that quantum rules could also enable a minuscule bubble of space itself to burst into being from nothing, with the impetus to then inflate to astronomical scales. Our cosmos could thus have been burped into being by the laws of physics alone. To Vilenkin, this result put an end to the question of what came before the Big Bang: nothing. Many cosmologists have made peace with the notion of a universe without a prime mover, divine or otherwise.

At the other end of the philosophical spectrum, I met with Don Page, a physicist and evangelical Christian at the University of Alberta in Canada, noted for his early collaboration with Stephen Hawking on the nature of black holes. To Page, the salient point is that God created the Universe ex nihilo – from absolutely nothing. The kind of cosmogenesis envisioned by Linde, in contrast, would require physicists to cook up their cosmos in a highly technical laboratory, using a far more powerful cousin of the Large Hadron Collider near Geneva. It would also require a seed particle called a ‘monopole’ (which is hypothesized to exist by some models of physics, but has yet to be found).

The idea goes that if we could impart enough energy to a monopole, it will start to inflate. Rather than growing in size within our Universe, the expanding monopole would bend spacetime within the accelerator to create a tiny wormhole tunnel leading to a separate region of space. From within our lab we would see only the mouth of the wormhole; it would appear to us as a mini black hole, so small as to be utterly harmless. But if we could travel into that wormhole, we would pass through a gateway into a rapidly expanding baby universe that we had created. (A video illustrating this process provides some further details.)

We have no reason to believe that even the most advanced physics hackers could conjure a cosmos from nothing at all, Page argues. Linde’s concept of cosmogenesis, audacious as it might be, is still fundamentally technological. Page, therefore, sees little threat to his faith. On this first issue, then, cosmogenesis would not necessarily upset existing theological views.

But flipping the problem around, I started to wonder: what are the implications of humans even considering the possibility of one day making a universe that could become inhabited by intelligent life? As I discuss in my book A Big Bang in a Little Room (2017), current theory suggests that, once we have created a new universe, we would have little ability to control its evolution or the potential suffering of any of its residents. Wouldn’t that make us irresponsible and reckless deities? I posed the question to Eduardo Guendelman, a physicist at Ben Gurion University in Israel, who was one of the architects of the cosmogenesis model back in the 1980s. Today, Guendelman is engaged in research that could bring baby-universe-making within practical grasp. I was surprised to find that the moral issues did not cause him any discomfort. Guendelman likens scientists pondering their responsibility over making a baby universe to parents deciding whether or not to have children, knowing they will inevitably introduce them to a life filled with pain as well as joy.

Other physicists are more wary. Nobuyuki Sakai of Yamaguchi University in Japan, one of the theorists who proposed that a monopole could serve as the seed for a baby universe, admitted that cosmogenesis is a thorny issue that we should ‘worry’ about as a society in the future. But he absolved himself of any ethical concerns today. Although he is performing the calculations that could allow cosmogenesis, he notes that it will be decades before such an experiment might feasibly be realized. Ethical concerns can wait.

Many of the physicists I approached were reluctant to wade into such potential philosophical quandaries. So I turned to a philosopher, Anders Sandberg at the University of Oxford, who contemplates the moral implications of creating artificial sentient life in computer simulations. He argues that the proliferation of intelligent life, regardless of form, can be taken as something that has inherent value. In that case, cosmogenesis might actually be a moral obligation.

Looking back on my numerous conversations with scientists and philosophers on these issues, I’ve concluded that the editors at Nuclear Physics B did a disservice both to physics and to theology. Their little act of censorship served only to stifle an important discussion. The real danger lies in fostering an air of hostility between the two sides, leaving scientists afraid to speak honestly about the religious and ethical consequences of their work out of concerns of professional reprisal or ridicule.

We will not be creating baby universes anytime soon, but scientists in all areas of research must feel able to freely articulate the implications of their work without concern for causing offense. Cosmogenesis is an extreme example that tests the principle. Parallel ethical issues are at stake in the more near-term prospects of creating artificial intelligence or developing new kinds of weapons, for instance. As Sandberg put it, although it is understandable that scientists shy away from philosophy, afraid of being thought weird for veering beyond their comfort zone, the unwanted result is that many of them keep quiet on things that really matter.

As I was leaving Linde’s office at Stanford, after we’d spent a day riffing on the nature of God, the cosmos and baby universes, he pointed at my notes and commented ruefully: ‘If you want to have my reputation destroyed, I guess you have enough material.’ This sentiment was echoed by a number of the scientists I had met, whether they identified as atheists, agnostics, religious or none of the above. The irony was that if they felt able to share their thoughts with each other as openly as they had with me, they would know that they weren’t alone among their colleagues in pondering some of the biggest questions of our being.Aeon counter – do not remove

 

This article was originally published at Aeon and has been republished under Creative Commons.

CATEGORIZED UNDER: Space & Physics, Top Posts
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The 4 Big Discoveries Underpinning Our Knowledge of the Universe

By Scott Bembenek | June 7, 2017 11:53 am
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Astronomers using the Hubble Space Telescope assembled a comprehensive view of the evolving universe. (Credit: NASA/ESA)

For many, science is nothing more than that class you were required to take in school. However, whether you realize it or not, science is all around us, and it impacts every aspect of our lives. And, the stories behind key scientific discoveries, though not commonly known, are truly inspiring.

So, if you want a quick refresher on how the universe works, focus on these four fascinating discoveries and the history behind them: Read More

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Can Math Can Save You From the Slow Line?

shutterstock_462351385

A sight we’ve all seen, but can we increase our odds of choosing the fastest line?

It seems obvious. You arrive at the checkouts and see one line is much longer than the other, so you join the shorter one. But, before long, the people in the bigger line zoom past you and you’ve barely moved toward the exit. The Conversation

When it comes to queuing, the intuitive choice is often not the fastest one. Why do lines feel like they slow down as soon as you join them? And is there a way to decide beforehand which line is really the best one to join? Mathematicians have been studying these questions for years. So can they help us spend less time waiting in line? Read More

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Is Technology Too Good for an Old-School Test of Einstein’s Relativity?

By Terena Bell | May 5, 2017 11:45 am
July 11, 2010 eclipse Image as viewed from Easter Island in the South Pacific. (Credits: Williams College Eclipse Expedition - Jay M. Pasachoff, Muzhou Lu, and Craig Malamut)

July 11, 2010 eclipse Image as viewed from Easter Island in the South Pacific. (Credits: Williams College Eclipse Expedition – Jay M. Pasachoff, Muzhou Lu, and Craig Malamut)

On Aug. 21, sky-gazers from around the world will converge in the United States as a total solar eclipse charts a path from Oregon to South Carolina. In between, on Casper Mountain in Wyoming, you’ll find Don Bruns with his telescope.

A retired physicist, Bruns is using the rare opportunity to test Albert Einstein’s general relativity like Sir Arthur Eddington, who was the first scientist to test the theory back in 1919. At that time, Newton’s law of universal gravity was still vogue, but Einstein shook the status quo by introducing his theory of general relativity, which fused concepts of time and three-dimensional space into a four-dimensional continuum called space-time. According to Einstein, gravity wasn’t a force; instead, it was a distortion in the fabric of space-time. Read More

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When Earth Became a ‘Mote of Dust’

By Shannon Stirone | February 14, 2017 12:28 pm
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Earth, seen as the faint dot in a sunbeam, is 4 billion miles away in this image from Voyager 1. (Credit: NASA/JPL)

We glimpsed Earth’s curvature in 1946, via a repurposed German V-2 rocket that flew 65 miles above the surface. Year-by-year, we climbed a little higher, engineering a means to comprehend the magnitude of our home.

In 1968, Apollo 8 lunar module pilot William Anders captured the iconic Earthrise photo. We contemplated the beauty of our home. Read More

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Has Dogma Derailed the Search for Dark Matter?

By Pavel Kroupa, University of Bonn | February 6, 2017 12:56 pm
dark-matter

A Hubble composite image shows a ring of ‘dark matter’ in the galaxy cluster Cl 0024+17. Courtesy NASA, ESA, M.J. Jee and H. Ford. (Credit: Johns Hopkins University)

According to mainstream researchers, the vast majority of the matter in the Universe is invisible: it consists of dark-matter particles that do not interact with radiation and cannot be seen through any telescope. The case for dark matter is regarded as so overwhelming that its existence is often reported as fact. Lately, though, cracks of doubt have started to appear. In July, the LUX experiment in South Dakota came up empty in its search for dark particles – the latest failure in a planet-wide, decades-long effort to find them. Some cosmic surveys also suggest that dark particles cannot be there, which is especially confounding since astronomical observations were the original impetus for the dark-matter hypothesis. Read More

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Real-Life Rogue One: How the Soviets Stole NASA’s Shuttle Plans

By Eric Betz | December 14, 2016 11:54 am
buran

An artist’s illustration of the Buran shuttle. (Credit: Wikimedia Commons)

In the decrepit ruins of a Cold War-era Kazakhstani hangar, buried beneath decades of detritus, there’s a spaceship that was once the last hope of the Soviet space empire.

And you’d be forgiven for confusing the Buran shuttles (Russian for “snowstorm”) with say, America’s iconic Space Shuttle Enterprise, which is proudly displayed in a Manhattan museum. Their shapes, sizes and technology are almost identical, apart from the sickle and hammer. Read More

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Could a Corpse Seed Life on Another Planet?

By William Herkewitz | October 25, 2016 10:40 am
an astronaut drifts through space

(Credit: Shutterstock)

One day, it’s bound to happen. An astronaut dies in space.

Maybe the death occurred en route to Mars. Maybe she was interstellar, on board solo spacecraft. Or maybe the body was thrust out an airlock, a burial at space.

That corpse (or the corpse’s spacecraft) could spend anywhere from decades to millions of years adrift. It would coast listlessly in the void, until the creeping tendrils of gravity eventually pulled it into a final touchdown. Likely this corpse will burn up in a star.

But lets say it lands on a planet. Could our corpse, like a seed on the wind, bring life to a new world? Read More

CATEGORIZED UNDER: Space & Physics, Top Posts

The Arrow of Time? It’s All in Our Heads

By Robert Lanza, Wake Forest University | September 26, 2016 9:45 am
time-arrow

(lassedesignen/Shutterstock)

Have you ever wondered why we age and grow old?

In the movie “The Curious Case of Benjamin Button,” Brad Pitt springs into being as an elderly man and ages in reverse. 

To the bafflement of scientists, the fundamental laws of physics have no preference for a direction in time, and work just as well for events going forward or going backward in time.  Yet, in the real world, coffee cools and cars break down. No matter how many times you look in the mirror, you’ll never see yourself grow younger. But if the laws of physics are symmetric with respect to time, then why do we experience reality with the arrow of time strictly directed from the past to the future?

A new paper just published in Annalen der Physik — which published Albert Einstein’s theories of special and general relativity — Dmitry Podolsky, a theoretical physicist now working on aging at Harvard University, and I explain how the arrow of time ‒ indeed time itself ‒ is directly related to the nature of the observer (that is, us).

Our paper shows that time doesn’t just exist “out there” ticking away from past to future, but rather is an emergent property that depends on the observer’s ability to preserve information about experienced events. Read More

CATEGORIZED UNDER: Space & Physics, Top Posts
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