Astronomy Now Home
Home Magazine Sky Chart Resources Store

On Sale Now!



The April 2014 issue of Astronomy Now is on sale! Order direct from our store (free 1st class post & to UK addresses). The Astronomy Now iPad/iPhone editions are now available worldwide in the iTunes store.



Top Stories



Earthshine used to test life detection method
...By imagining the Earth as an exoplanet, scientists observing our planet's reflected light on the Moon with ESO's Very Large Telescope have demonstrated a way to detect life on other worlds...
  READ MORE

Solid buckyballs discovered in space
...Astronomers using NASA’s Spitzer Space Telescope have detected a particular type of molecule, given the nickname “buckyball”, in a solid form for the first time...
  READ MORE

Steamy water-world gets the Hubble treatment
...Hubble Space Telescope observations of a 7 Earth-mass planet find an unusual water-rich world swathed in a thick, steamy atmosphere...
  READ MORE








Liquid water on Mars
might taste salty

DR EMILY BALDWIN
ASTRONOMY NOW
Posted: 04 August 2011


Bookmark and Share

Fingers of dark material running down steep slopes in the warmest regions of Mars could be the result of salty water flows, say scientists interpreting repeat observations snapped by Mars Reconnaissance Orbiter's (MRO) powerful HiRISE camera.


An image combining orbital imagery with 3-D modeling shows flows that appear in spring and summer on a slope inside Mars' Newton crater. Image: NASA/JPL-Caltech/University of Arizona.

The dark stripes, which are on the order of a few metres wide and several hundred metres long, were identified on several steep equator-facing slopes in the middle latitudes of the red planet's southern hemisphere. The features are different to the much wider gullies already seen on many cold, pole-facing slopes, and appear to fade during the winter months, reappearing in springtime. In some locations more than 1,000 individual flows have been identified, some of which had grown by more than 200 metres in just two Earth months.

“But the sites themselves are rare,” says Alfred McEwen of the University of Arizona's Lunar and Planetary Laboratory, principal investigator of HiRISE and lead author of a paper reporting the results in the latest edition of the journal Science. “We have seven individual sites confirmed, with 20 candidates waiting to be confirmed in repeat imaging.”

In one location, the pattern is repeated over three martian summers. “A volatile material is likely involved in the activity,” says McEwen. The scientists suspect the flows might be briny, which is consistent with the detection of salt deposits in many locations over Mars’ surface. Salt lowers the freezing temperature of water, so although the temperatures observed would not melt pure water ice, the salt content of this fluid – saltier than Earth's oceans – is enough to keep the water liquid. Yet MRO's Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) has, to date, not found any indication of water at these sites.

"It's a mystery now, but I think it's a solvable mystery with further observations and laboratory experiments," says McEwen. “It’s the first time we’ve seen the potential for water; it might be salty, but it’s liquid.”


This image shows warm-season flows on a north-facing slope in middle southern latitudes of Mars. Repeat imaging by HiRISE shows the features appear and incrementally grow during warm seasons and fade in cold seasons. Image: NASA/JPL-Caltech/University of Arizona.

On Earth, where there’s water, there’s life, and NASA’s mantra of “follow the water” to find life has stepped up a gear with this discovery. Evidence for ancient rivers and lakes exist all over Mars, and sites which potentially host liquid brines will help in the quest to determine whether life exists, or once existed, on the planet. Frozen water is widespread, and ice has been detected in freshly formed shallow impact craters and seen in trenches dug by the Phoenix Mars Lander near the planet's north pole, for example. Furthermore, beads of droplets seen on Phoenix's landing struts were argued to be globules of brine-rich liquid. Landslides seen in gullies are also thought to have been facilitated by flowing water.

“The mid-latitudes are turning out to be the place on Mars where a lot of the action is,” says Philip Christensen, a geophysicist at Arizona State University. “The new discovery provides evidence that water is closer to the equator than previously thought, which has the potential to be liquid at various times throughout the year. We’re now at the beginning of a scientific process to probe the details.”

Until that crucial direct detection is made, this is surely the best evidence yet of liquid water flowing on Mars.

The Planets
From tiny Mercury to distant Neptune and Pluto, The Planets profiles each of the Solar System's members in depth, featuring the latest imagery from space missions. The tallest mountains, the deepest canyons, the strongest winds, raging atmospheric storms, terrain studded with craters and vast worlds of ice are just some of the sights you'll see on this 100-page tour of the planets.
 GET YOUR COPY

Hubble Reborn
Hubble Reborn takes the reader on a journey through the Universe with spectacular full-colour pictures of galaxies, nebulae, planets and stars as seen through Hubble's eyes, along the way telling the dramatic story of the space telescope, including interviews with key scientists and astronauts.
 GET YOUR COPY

3D Universe
Witness the most awesome sights of the Universe as they were meant to be seen in this 100-page extravaganza of planets, galaxies and star-scapes, all in 3D!
 GET YOUR COPY


HOME | NEWS ARCHIVE | MAGAZINE | SOLAR SYSTEM | SKY CHART | RESOURCES | STORE | SPACEFLIGHT NOW

© 2014 Pole Star Publications Ltd.