Astrobiology

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Autumn Garden by Boris Groh

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The Milky Way’s long-lost sibling finally found

Scientists at the University of Michigan have deduced that the Andromeda galaxy, our closest large galactic neighbor, shredded and cannibalized a massive galaxy two billion years ago.

Even though it was mostly shredded, this massive galaxy left behind a rich trail of evidence: an almost invisible halo of stars larger than the Andromeda galaxy itself, an elusive stream of stars and a separate enigmatic compact galaxy, M32. Discovering and studying this decimated galaxy will help astronomers understand how disk galaxies like the Milky Way evolve and survive large mergers.

This disrupted galaxy, named M32p, was the third-largest member of the Local Group of galaxies, after the Milky Way and Andromeda galaxies. Using computer models, Richard D'Souza and Eric Bell of the University of Michigan’s Department of Astronomy were able to piece together this evidence, revealing this long-lost sibling of the Milky Way. Their findings were published in Nature Astronomy.

source

The diversity of worlds in our solar system (climate and geology)…

The Great Red Spot is a persistent high-pressure region in the atmosphere of Jupiter, producing an anticyclonic storm 22° south of the planet’s equator. It has been continuously observed for 188 years, since 1830. Earlier observations from 1665 to 1713 are believed to be of the same storm; if this is correct, it has existed for at least 350 years. Such storms are not uncommon within the turbulent atmospheres of gas giants.

With over 400 active volcanoes, Io is the most geologically active object in the Solar System. This extreme geologic activity is the result of tidal heating from friction generated within Io’s interior as it is pulled between Jupiter and the other Galilean satellites—Europa, Ganymede and Callisto.

Europa has the smoothest surface of any known solid object in the Solar System. The apparent youth and smoothness of the surface have led to the hypothesis that a water ocean exists beneath it, which could conceivably harbor extraterrestrial life.

Neptune, the eighth and farthest planet from the sun, has the strongest winds in the solar system. At high altitudes speeds can exceed 1,100 mph. That is 1.5 times faster than the speed of sound. In 1989, NASA’s Voyager 2 spacecraft made the first and only close-up observations of Neptune.

Ganymede  is the largest and most massive moon of Jupiter and in the Solar System. Possessing a metallic core, it has the lowest moment of inertia factor of any solid body in the Solar System and is the only moon known to have a magnetic field. (Sounds of Ganymede’s magnetosphere).

Saturn’s hexagon is a persisting hexagonal cloud pattern around the north pole of Saturn, located at about 78°N. The sides of the hexagon are about 13,800 km (8,600 mi) long, which is more than the diameter of Earth (about 12,700 km (7,900 mi)).

Miranda’s surface has patchwork regions of broken terrain indicating intense geological activity in Miranda’s past, and is criss-crossed by huge canyons. It also has the largest known cliff in the Solar System, Verona Rupes, which has a height of over 5 km (3.1 mi). 

Some of Miranda’s terrain is possibly less than 100 million years old based on crater counts, which suggests that Miranda may still be geologically active today.

Enceladus is the sixth-largest moon of Saturn. It is about 500 kilometers (310 mi) in diameter, about a tenth of that of Saturn’s largest moon, Titan.  Evidence of liquid water on Enceladus began to accumulate in 2005, when scientists observed plumes containing water vapor spewing from its south polar surface, with jets moving 250 kg of water vapor every second at up to 2,189 km/h (1,360 mph) into space.

Titan is the largest moon of Saturn. It is the only moon known to have a dense atmosphere, and the only object in space, other than Earth, where clear evidence of stable bodies of surface liquid has been found.

Triton is one of the few moons in the Solar System known to be geologically active (the others being Jupiter’s Io and Europa, and Saturn’s Enceladus and Titan). As a consequence, its surface is relatively young with few obvious impact craters, and a complex geological history revealed in intricate cryovolcanic and tectonic terrains. Part of its surface has geysers erupting sublimated nitrogen gas, contributing to a tenuous nitrogen atmosphere less than 1/70,000 the pressure of Earth’s atmosphere at sea level.

source: wikipedia~

image credit: data and images from NASA

Frozen: Ice on Earth and Well Beyond

Icy Hearts: A heart-shaped calving front of a glacier in Greenland (left) and Pluto’s frozen plains (right). Credits: NASA/Maria-Jose Viñas and NASA/APL/SwRI

From deep below the soil at Earth’s polar regions to Pluto’s frozen heart, ice exists all over the solar system…and beyond. From right here on our home planet to moons and planets millions of miles away, we’re exploring ice and watching how it changes. Here’s 10 things to know:

1. Earth’s Changing Ice Sheets

An Antarctic ice sheet. Credit: NASA

Ice sheets are massive expanses of ice that stay frozen from year to year and cover more than 6 million square miles. On Earth, ice sheets extend across most of Greenland and Antarctica. These two ice sheets contain more than 99 percent of the planet’s freshwater ice. However, our ice sheets are sensitive to the changing climate.

Data from our GRACE satellites show that the land ice sheets in both Antarctica and Greenland have been losing mass since at least 2002, and the speed at which they’re losing mass is accelerating.

2. Sea Ice at Earth’s Poles

Earth’s polar oceans are covered by stretches of ice that freezes and melts with the seasons and moves with the wind and ocean currents. During the autumn and winter, the sea ice grows until it reaches an annual maximum extent, and then melts back to an annual minimum at the end of summer. Sea ice plays a crucial role in regulating climate – it’s much more reflective than the dark ocean water, reflecting up to 70 percent of sunlight back into space; in contrast, the ocean reflects only about 7 percent of the sunlight that reaches it. Sea ice also acts like an insulating blanket on top of the polar oceans, keeping the polar wintertime oceans warm and the atmosphere cool.

Some Arctic sea ice has survived multiple years of summer melt, but our research indicates there’s less and less of this older ice each year. The maximum and minimum extents are shrinking, too. Summertime sea ice in the Arctic Ocean now routinely covers about 30-40 percent less area than it did in the late 1970s, when near-continuous satellite observations began. These changes in sea ice conditions enhance the rate of warming in the Arctic, already in progress as more sunlight is absorbed by the ocean and more heat is put into the atmosphere from the ocean, all of which may ultimately affect global weather patterns.

3. Snow Cover on Earth

Snow extends the cryosphere from the poles and into more temperate regions.

Snow and ice cover most of Earth’s polar regions throughout the year, but the coverage at lower latitudes depends on the season and elevation. High-elevation landscapes such as the Tibetan Plateau and the Andes and Rocky Mountains maintain some snow cover almost year-round. In the Northern Hemisphere, snow cover is more variable and extensive than in the Southern Hemisphere.

Snow cover the most reflective surface on Earth and works like sea ice to help cool our climate. As it melts with the seasons, it provides drinking water to communities around the planet.

4. Permafrost on Earth

Tundra polygons on Alaska’s North Slope. As permafrost thaws, this area is likely to be a source of atmospheric carbon before 2100. Credit: NASA/JPL-Caltech/Charles Miller

Permafrost is soil that stays frozen solid for at least two years in a row. It occurs in the Arctic, Antarctic and high in the mountains, even in some tropical latitudes. The Arctic’s frozen layer of soil can extend more than 200 feet below the surface. It acts like cold storage for dead organic matter – plants and animals.

In parts of the Arctic, permafrost is thawing, which makes the ground wobbly and unstable and can also release those organic materials from their icy storage. As the permafrost thaws, tiny microbes in the soil wake back up and begin digesting these newly accessible organic materials, releasing carbon dioxide and methane, two greenhouse gases, into the atmosphere.

Two campaigns, CARVE and ABoVE, study Arctic permafrost and its potential effects on the climate as it thaws.

5. Glaciers on the Move

Did you know glaciers are constantly moving? The masses of ice act like slow-motion rivers, flowing under their own weight. Glaciers are formed by falling snow that accumulates over time and the slow, steady creep of flowing ice. About 10 percent of land area on Earth is covered with glacial ice, in Greenland, Antarctica and high in mountain ranges; glaciers store much of the world’s freshwater.

Our satellites and airplanes have a bird’s eye view of these glaciers and have watched the ice thin and their flows accelerate, dumping more freshwater ice into the ocean, raising sea level.

6. Pluto’s Icy Heart

The nitrogen ice glaciers on Pluto appear to carry an intriguing cargo: numerous, isolated hills that may be fragments of water ice from Pluto’s surrounding uplands. NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute

Pluto’s most famous feature – that heart! – is stone cold. First spotted by our New Horizons spacecraft in 2015, the heart’s western lobe, officially named Sputnik Planitia, is a deep basin containing three kinds of ices – frozen nitrogen, methane and carbon monoxide.

Models of Pluto’s temperatures show that, due the dwarf planet’s extreme tilt (119 degrees compared to Earth’s 23 degrees), over the course of its 248-year orbit, the latitudes near 30 degrees north and south are the coldest places – far colder than the poles. Ice would have naturally formed around these latitudes, including at the center of Sputnik Planitia.

New Horizons also saw strange ice formations resembling giant knife blades. This “bladed terrain” contains structures as tall as skyscrapers and made almost entirely of methane ice, likely formed as erosion wore away their surfaces, leaving dramatic crests and sharp divides. Similar structures can be found in high-altitude snowfields along Earth’s equator, though on a very different scale.

7. Polar Ice on Mars

This image, combining data from two instruments aboard our Mars Global Surveyor, depicts an orbital view of the north polar region of Mars. Credit: NASA/JPL-Caltech/MSSS

Mars has bright polar caps of ice easily visible from telescopes on Earth. A seasonal cover of carbon dioxide ice and snow advances and retreats over the poles during the Martian year, much like snow cover on Earth.

This animation shows a side-by-side comparison of CO2 ice at the north (left) and south (right) Martian poles over the course of a typical year (two Earth years). This simulation isn’t based on photos; instead, the data used to create it came from two infrared instruments capable of studying the poles even when they’re in complete darkness. This data were collected by our Mars Reconnaissance Orbiter, and Mars Global Surveyor. Credit: NASA/JPL-Caltech

During summertime in the planet’s north, the remaining northern polar cap is all water ice; the southern cap is water ice as well, but remains covered by a relatively thin layer of carbon dioxide ice even in summertime.

Scientists using radar data from our Mars Reconnaissance Orbiter found a record of the most recent Martian ice age in the planet’s north polar ice cap. Research indicates a glacial period ended there about 400,000 years ago. Understanding seasonal ice behavior on Mars helps scientists refine models of the Red Planet’s past and future climate.

8. Ice Feeds a Ring of Saturn

Wispy fingers of bright, icy material reach tens of thousands of kilometers outward from Saturn’s moon Enceladus into the E ring, while the moon’s active south polar jets continue to fire away. Credit: NASA/JPL/Space Science Institute

Saturn’s rings and many of its moons are composed of mostly water ice – and one of its moons is actually creating a ring. Enceladus, an icy Saturnian moon, is covered in “tiger stripes.” These long cracks at Enceladus’ South Pole are venting its liquid ocean into space and creating a cloud of fine ice particles over the moon’s South Pole. Those particles, in turn, form Saturn’s E ring, which spans from about 75,000 miles (120,000 kilometers) to about 260,000 miles (420,000 kilometers) above Saturn’s equator. Our Cassini spacecraft discovered this venting process and took high-resolution images of the system.

Jets of icy particles burst from Saturn’s moon Enceladus in this brief movie sequence of four images taken on Nov. 27, 2005. Credit: NASA/JPL/Space Science Institute

9. Ice Rafts on Europa

View of a small region of the thin, disrupted, ice crust in the Conamara region of Jupiter’s moon Europa showing the interplay of surface color with ice structures. Credit: NASA/JPL/University of Arizona

The icy surface of Jupiter’s moon Europa is crisscrossed by long fractures. During its flybys of Europa, our Galileo spacecraft observed icy domes and ridges, as well as disrupted terrain including crustal plates that are thought to have broken apart and “rafted” into new positions. An ocean with an estimated depth of 40 to 100 miles (60 to 150 kilometers) is believed to lie below that 10- to 15-mile-thick (15 to 25 km) shell of ice.

The rafts, strange pits and domes suggest that Europa’s surface ice could be slowly turning over due to heat from below. Our Europa Clipper mission, targeted to launch in 2022, will conduct detailed reconnaissance of Europa to see whether the icy moon could harbor conditions suitable for life.

10. Crater Ice on Our Moon

The image shows the distribution of surface ice at the Moon’s south pole (left) and north pole (right), detected by our Moon Mineralogy Mapper instrument. Credit: NASA

In the darkest and coldest parts of our Moon, scientists directly observed definitive evidence of water ice. These ice deposits are patchy and could be ancient. Most of the water ice lies inside the shadows of craters near the poles, where the warmest temperatures never reach above -250 degrees Fahrenheit. Because of the very small tilt of the Moon’s rotation axis, sunlight never reaches these regions.

A team of scientists used data from a our instrument on India’s Chandrayaan-1 spacecraft to identify specific signatures that definitively prove the water ice. The Moon Mineralogy Mapper not only picked up the reflective properties we’d expect from ice, but was able to directly measure the distinctive way its molecules absorb infrared light, so it can differentiate between liquid water or vapor and solid ice.

With enough ice sitting at the surface – within the top few millimeters – water would possibly be accessible as a resource for future expeditions to explore and even stay on the Moon, and potentially easier to access than the water detected beneath the Moon’s surface.

11. Bonus: Icy World Beyond Our Solar System!

With an estimated temperature of just 50K, OGLE-2005-BLG-390L b is the chilliest exoplanet yet discovered. Pictured here is an artist’s concept. Credit: NASA

OGLE-2005-BLG-390Lb, the icy exoplanet otherwise known as Hoth, orbits a star more than 20,000 light years away and close to the center of our Milky Way galaxy. It’s locked in the deepest of deep freezes, with a surface temperature estimated at minus 364 degrees Fahrenheit (minus 220 Celsius)!

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If you’ve visited the Museum, you’re certainly familiar with today’s Fossil Friday feature: the Barosaurus and Allosaurus in the Rotunda! Rising 50 ft (15 m) above the ground, it’s the world’s tallest freestanding dinosaur mount. In this scene, a Barosaurus rears up to defend her young from an Allosaurus. How does the huge skeleton of Barosaurus—whose name means “heavy reptile”—stay up? The Barosaurus is built from casts of real fossil bones, while the originals are housed in the Museum’s collections. Real fossil bones would be too heavy to support this way.

Photo: D. Finnin / © AMNH