Planets that can potentially support life... - Page 40

Saturn's moon Enceladus is a mystery. From Earth it looks tiny and cold, and yet it's not a dead hunk of rock. Passing spacecraft see trenches and ridges, similar to Earth's, and in 2005 NASA's Cassini mission spotted ice geysers streaming from its south pole.

"The moon is actually alive in a sense," says Sean Hsu with the Laboratory for Atmospheric and Space Physics at the University of Colorado at Boulder.

Beneath the surface, most researchers believe it even has a liquid ocean. Now Hsu and his colleagues have found new evidence that it's a downright balmy ocean.

The team used the Cassini spacecraft, which orbits Saturn, to detect tiny particles of silica floating in space. It's not sand exactly, but researchers think the particles did come from the bottom of Enceladus' ocean.

The silica particles could only be made if that ocean were hot. "We think that the temperature at least in some part of the ocean must be higher than 190 degrees Fahrenheit," Hsu says. "If you could swim a little bit further from the really hot part then it could be comfy."

In fact, 190°F is cooler than many hydrothermal vents at the bottom of Earth's oceans. Hsu says experiments on Earth also suggest the ocean is similar in salinity and pH to oceans here.

The evidence, published in the journal Nature, is somewhat circumstantial. The theory is that the silica formed and then dissolved in seawater beneath Enceladus' icy crust. It then left the moon through geysers, and filled Saturn's E-ring. From the E-ring, the silica eventually wound up in the giant planet's magnetosphere, which is where Cassini saw it.

"It's not like they flew through the plumes of Enceladus and measured these particles," says Bill McKinnon, a planetary scientist at Washington University in St. Louis.

Nevertheless, he and other independent researchers think the hypothesis has a reasonable chance of being right. "It's very hard to make silica in the Saturn system except if you have a warm wet environment," says John Spencer, a researcher at the Southwest Research Institute in Boulder, Colo. Enceladus is the most likely place.

Why is tiny Enceladus so warm? Spencer suspects it's the gravitational pull of Saturn and some of its other moons. Their attraction could tug the water and rock inside Enceladus, causing it to slosh around and heat up.

But current models show that gravity alone can't explain the warm oceans, says McKinnon. He thinks something else could be generating that energy.

On July 07 2014 09:59 MarlieChurphy wrote:
Sad update http://www.universityherald.com/articles/10259/20140705/study-disproves-existence-of-2-earth-like-planets-has-scientists-hopeful-for-future-exoplanet-searches.htm

Jupiter’s largest moon, Ganymede, has solidified its membership in the growing cadre of solar system locales where liquid water flows beneath the surface.

“The solar system is now looking like a pretty soggy place,” Jim Green, director of NASA’s Planetary Science Division, said March 12 at a news conference.

The ocean showed itself not with plumes or pools but via subtle changes in Ganymede’s aurora, the moon’s version of the Northern Lights. Jupiter’s magnetic field should interfere with Ganymede’s, causing the moon’s aurora to rock back and forth by about 6 degrees. Observations with the Hubble Space Telescope, however, showed that the aurora shifted by only about 2 degrees. Joachim Saur, a geophysicist at the University of Cologne, Germany, and colleagues deduced that an electrically conductive fluid beneath the surface — a saltwater ocean, for example — would create a secondary magnetic field that counteracted Jupiter’s interference.

Astronomers have spotted the closest thing yet to the first true ‘Earth twin’ — a small planet orbiting the bright star Kepler 452, at a distance where liquid water could exist.

“It is the first terrestrial planet in the habitable zone around a star very similar to the Sun,” says Douglas Caldwell, an astronomer at the SETI Institute in Mountain View, California.

The alien world is 60% larger than Earth and orbits its star at a distance similar to that between Earth and the Sun. The star itself lies 430 parsecs from Earth, in the constellation Cygnus. It is slightly brighter than the Sun, making its planet a better Earth analogue than planets announced last year and in January, both of which orbited dim, cool stars.

NASA announced the planet, dubbed Kepler-452b, on 23 July, as part of the latest harvest of worlds spotted by its Kepler spacecraft. From 2009 to 2013, Kepler stared at a small patch of sky looking for slight decreases in starlight that signalled a planet moving across the face of a star. The spacecraft has discovered more than 1,000 confirmed planets, including Kepler-452b, and more than 4,660 candidates.

The latest batch includes 11 other candidate planets that are all less than twice the diameter of Earth and orbit in their stars’ habitable zones, says Natalie Batalha, Kepler's mission scientist and an astronomer at NASA's Ames Research Center in Moffett Field, California.

Astronomers say three recently discovered planets similar to Earth’s size and temperature may have conditions that could sustain life.

An international team observed the three planets orbiting a reddish, ultracool dwarf star, once thought too dim to anchor a solar system. Their research, published in the journal Nature on Monday, said these are the first planets ever seen orbiting an ultracool dwarf star.

“Systems around these tiny stars are the only places where we can detect life on an Earth-sized exoplanet with our current technology,” co-author Michael Gillon, of the University of Liege in Belgium, said in a statement. “So if we want to find life elsewhere in the universe, this is where we should start to look.”

Previously, scientists have only found exoplanets — planets that do not orbit our sun — with conditions unlike Earth’s. In November, for instance, a rocky, Earth-sized planet was found 39 light years away, but its temperature was estimated at 300 degrees to 600 degrees. The discovery of the three potentially habitable planets may encourage researchers to look more closely at the huge numbers of ultracool dwarf stars.

The three planets orbit a star in the Aquarius constellations named Trappist-1, which is about the size of Jupiter. But the planets are close enough to the star to have “temperate” conditions on their surface, MIT researcher Julien De Wit told NPR.

Astronomers using NASA's Hubble Space Telescope have imaged what may be water vapor plumes erupting off the surface of Jupiter's moon Europa. This finding bolsters other Hubble observations suggesting the icy moon erupts with high altitude water vapor plumes.

The observation increases the possibility that missions to Europa may be able to sample Europa's ocean without having to drill through miles of ice.

"Europa's ocean is considered to be one of the most promising places that could potentially harbor life in the solar system," said Geoff Yoder, acting associate administrator for NASA's Science Mission Directorate in Washington. "These plumes, if they do indeed exist, may provide another way to sample Europa's subsurface."

The plumes are estimated to rise about 125 miles (200 kilometers) before, presumably, raining material back down onto Europa's surface. Europa has a huge global ocean containing twice as much water as Earth's oceans, but it is protected by a layer of extremely cold and hard ice of unknown thickness. The plumes provide a tantalizing opportunity to gather samples originating from under the surface without having to land or drill through the ice.

The team, led by William Sparks of the Space Telescope Science Institute (STScI) in Baltimore observed these finger-like projections while viewing Europa's limb as the moon passed in front of Jupiter.

The original goal of the team's observing proposal was to determine whether Europa has a thin, extended atmosphere, or exosphere. Using the same observing method that detects atmospheres around planets orbiting other stars, the team realized if there was water vapor venting from Europa's surface, this observation would be an excellent way to see it.

"The atmosphere of an extrasolar planet blocks some of the starlight that is behind it," Sparks explained. "If there is a thin atmosphere around Europa, it has the potential to block some of the light of Jupiter, and we could see it as a silhouette. And so we were looking for absorption features around the limb of Europa as it transited the smooth face of Jupiter."

In 10 separate occurrences spanning 15 months, the team observed Europa passing in front of Jupiter. They saw what could be plumes erupting on three of these occasions.

A rocky planet discovered in the "habitable" zone of the star nearest our Sun may be covered with oceans, researchers at France's CNRS research institute said Thursday.

A team including CNRS astrophysicists have calculated the size and surface properties of the planet dubbed Proxima b, and concluded it may be an "ocean planet" similar to Earth.

Scientists announced Proxima b's discovery in August, and said it may be the first exoplanet—planet outside our Solar System—to one day be visited by robots from Earth.

The planet orbits within a "temperate" zone from its host star Proxima Centauri, some four light years from us.

It is estimated to have a mass about 1.3 times that of Earth, and orbits about 7.5 million kilometres (4.6 million miles) from its star—about a tenth the distance of innermost planet Mercury from the Sun.

"Contrary to what one might expect, such proximity does not necessarily mean that Proxima b's surface is too hot" for water to exist in liquid form, said a CNRS statement.

Proxima Centauri is smaller and 1,000 times weaker than our Sun, which means Proxima b is at exactly the right distance for conditions to be potentially habitable.

"The planet may very well host liquid water on its surface, and therefore also some forms of life," the statement said.

The size of exoplanets are generally calculated by measuring how much light they block out, from Earth's perspective, when they pass in front of their host star.

But no such transit of Proxima b has yet been observed, so the team had to rely on simulations to estimate the planet's composition and radius.

On October 04 2016 09:50 FiWiFaKi wrote:


I fail to see the gravity problem you're talking about (but I don't look at this much)

Gravitation force is m/r^2... So a planet with say 4x Earth mass... You have V = 1.333pi*r^3, so 4x volume results in radius 4^0.333 larger.

And so you get 1.587x the gravity of the Earth. I'm not expert, but I do see why life couldn't exist at 2x, or even 3x of current gravity. Sure, humans would have a tougher time, but life, no... We have fish living in deep sea oceans where the pressure is so immense, and they are okay. Plus, I believe that earth is denser than most of the planets looked at, so the gravity would be even lower than in my approximation.

Just from intuition, I'm fairly sure that our bodies could adapt to handle 20m/s^2 acceleration due to gravity.

edit: Heck, the only two planets that have gravity higher than earth on their surface is Neptune with 1.12x, and Jupiter with 2.36x. I think we have little worry about it.