Tag: Remote Sensing

Ancient ‘Blue’ Mars Lost an Entire Ocean to Space


Artist impression of Mars ocean

Excerpt from news.discovery.com

Mars was once a small, wet and blue world, but over the past 4 billion years, Mars dried up and became the red dust bowl we know today.

But how much water did Mars possess? According to research published in the journal Science, the Martian northern hemisphere was likely covered in an ocean, covering a region of the approximate area as Earth’s Atlantic Ocean, plunging, in some places, to 1.6 kilometers (1 mile) deep.

“Our study provides a solid estimate of how much water Mars once had, by determining how much water was lost to space,” said Geronimo Villanueva, of NASA’s Goddard Space Flight Center in Greenbelt, Maryland, and lead author of the new paper, in an ESO news release. “With this work, we can better understand the history of water on Mars.”

Over a 6-year period, Villanueva and his team used the ESO’s Very Large Telescope (in Chile) and instruments at the W. M. Keck Observatory and the NASA Infrared Telescope Facility (both on Mauna Kea in Hawaii) to study the distribution of water molecules in the Martian atmosphere. By building a comprehensive map of water distribution and seasonal changes, they were able to arrive at this startling conclusion.

It is becoming clear that, over the aeons, Mars lost the majority of its atmosphere to space. That also goes for its water. Though large quantities of water were likely frozen below the surface as the atmosphere thinned and cooled, the water contained in an ocean of this size must have gone elsewhere — it must have also been lost to space.

This artist’s impression shows how Mars may have looked about four billion years ago. The young planet Mars would have had enough water to cover its entire surface in a liquid layer about 140 meters deep, but it is more likely that the liquid would have pooled to form an ocean occupying almost half of Mars’s northern hemisphere. 
The water in Earth’s oceans contains molecules of H2O, the familiar oxygen atom bound with 2 hydrogen atoms, and, in smaller quantities, the not-so-familiar HDO molecule. HDO is a type of water molecule that contains 1 hydrogen atom, 1 oxygen atom and 1 deuterium atom. The deuterium atom is an isotope of hydrogen; whereas hydrogen consists of 1 proton and an electron, deuterium consists of 1 proton, 1 neutron and 1 electron. Therefore, due to the extra neutron the deuterium contains, HDO molecules are slightly heavier than the regular H2O molecules.

Also known as “semi-heavy water,” HDO is less susceptible to being evaporated away and being lost to space, so logic dictates that if water is boiled (or sublimated) away on Mars, the H2O molecules will be preferentially lost to space whereas a higher proportion of HDO will be left behind.

By using powerful ground-based observatories, the researchers were able to determine the distribution of HDO molecules and the H2O molecules and compare their ratios to liquid water that is found in its natural state.

Of particular interest is Mars’ north and south poles where icecaps containing water and carbon dioxide ice persist to modern times. The water those icecaps contain is thought to document the evolution of water since the red planet’s wet Noachian period (approximately 3.7 billion years ago) to today. It turns out that the water measured in these polar regions is enriched with HDO by a factor of 7 when compared with water in Earth’s oceans. This, according to the study, indicates that Mars has lost a volume of water 6.5 times larger than the water currently contained within the modern-day icecaps.

Therefore, the volume of Mars’ early ocean must have been at least 20 million cubic kilometers, writes the news release.

Taking into account the Martian global terrain, most of the water would have been concentrated around the northern plains, a region dominated by low-lying land. An ancient ocean, with this estimate volume of water, would have covered 19 percent of the Martian globe, a significant area considering the Atlantic Ocean covers 17 percent of the Earth’s surface.

“With Mars losing that much water, the planet was very likely wet for a longer period of time than previously thought, suggesting the planet might have been habitable for longer,” said Michael Mumma, also of NASA’s Goddard Space Flight Center.

This estimate is likely on the low-side as Mars is thought to contain significant quantities of water ice below its surface — a fact that surveys such as this can be useful for pinpointing exactly where the remaining water may be hiding.

Ulli Kaeufl, of the European Southern Observatory and co-author of the paper, added: “I am again overwhelmed by how much power there is in remote sensing on other planets using astronomical telescopes: we found an ancient ocean more than 100 million kilometers away!”
Source: ESO

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The Mission to land robot on comet to take final step







Excerpt from  theglobeandmail.com
By Ivan Semeniuk

Half a billion kilometres from Earth and 10 years into its remarkable journey, a small robot is about to plunge into space history.

Pending a final green light from mission controllers on Tuesday night, the robot – nicknamed Philae (fee-lay) – will detach from its mother ship and try to hook itself onto one of the most challenging and mysterious objects in the solar system.



It’s a high-risk manoeuvre with plenty of unknowns. But if it works, then the probe will be able to show us what no one has ever experienced: what it’s like to stand on the surface of a comet.

“Comets are new territory,” said Ralf Gellert, a professor of physics at the University of Guelph. “There could be some big surprises.”

Prof. Gellert should know. Fifteen years ago, he helped build one of the instruments on the dishwasher-size lander that will reveal the comet’s composition. No such direct measurement has been made before. Even designing how the instrument should work was fraught with challenges since there was so little known about what kind of surface the lander might find itself on.

“Is it an ice ball with rock and trace metals, or a rock ball with ice on it … or ice below the surface? We didn’t know,” he said.
And scientists still don’t.

When the European Space Agency launched the Rosetta mission in 2004, the mission’s target – Comet Churyumov-Gerasimenko – was little more than a fuzzy blip in astronomers’ telescopes. But Rosetta just arrived in August and it’s been in orbit around the comet since then.

What was assumed to be a single, homogeneous lump of ice and rock has turned out to be a bizarre-looking object in two parts, arranged a bit like the head and body of a rubber duck. By October, scientists had zeroed in on the head portion, which is four kilometres across at its widest point, and settled on a landing site.

Remote sensing data from Rosetta suggest that the comet is quite porous, with a surface that is as black as coal and somewhat warmer than expected. In other words, Philae will probably not be landing on skating-rink-hard ice. Yet, whether the surface will be crusty like a roadside snowbank, fluffy like cigarette ash, or something else entirely is anyone’s guess.

And while scientists and engineers say they’ve done everything they can think of to maximize the lander’s chance of success, they acknowledge it’s entirely possible that Philae will encounter something it can’t handle and smash to bits or sink into oblivion.


Yet the landing is more than a daring jaunt to see what has never been seen before. Comets are also among the most primitive bodies in the solar system. Each one is an amalgam of ice and rock that has been around since Earth and its sister planets formed billions of years ago. In a sense, comets are the leftovers of that process – primordial fossils from the birth of the solar system.

The instrument Prof. Gellert worked on, known as the alpha particle X-ray spectrometer (APXS), will help illuminate this early period by making precise measurements of the comet’s elemental ingredients.

It is carried on a robot arm that will place a radioactive source near the comet’s surface. The particles and X-rays the comet material gives off as a result of this exposure will provide detailed information about what chemical elements the comet contains. This will be augmented by another experiment designed to drill and extract a comet sample for analysis inside the lander.

Prof. Gellert, who has also been closely involved in NASA’s Mars rover missions, said Rosetta’s long timeline and the many unknowns related to the comet makes this week’s landing a trickier proposition than landing on Mars – but also a tremendously exciting one.

“I think it’s a matter of hope for the best and see what happens.”

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James Gilliland. – The Last Book on UFOs

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