Europa's salty lakes may harbour simple life forms - video

Jupiter's moon Europa is thought to have a vast ocean beneath its frozen surface.

NASA Cassini and other past missions have shown proof of salty water, which from our experience, has life-bearing potential.

Exploration of Europa is still stated as a high priority for NASA and is definitely a place of interest for science.

The video is presented by Kevin Hand, Astrobiologist and Deputy Chief Scientist at JPL.

The puzzling, fascinating surface of Jupiter's icy moon Europa looms large in this newly-reprocessed colour view, made from images taken by NASA's Galileo spacecraft in the late 1990s. 

This is the colour view of Europa from Galileo that shows the largest portion of the moon's surface at the highest resolution. 

The view was previously released as a mosaic with lower resolution and strongly enhanced colour. 

To create this new version, the images were assembled into a realistic colour view of the surface that approximates how Europa would appear to the human eye. 

The scene shows the stunning diversity of Europa's surface geology. Long, linear cracks and ridges crisscross the surface, interrupted by regions of disrupted terrain where the surface ice crust has been broken up and re-frozen into new patterns. 

Colour variations across the surface are associated with differences in geologic feature type and location. 

For example, areas that appear blue or white contain relatively pure water ice, while reddish and brownish areas include non-ice components in higher concentrations. 

The polar regions, visible at the left and right of this view, are noticeably bluer than the more equatorial latitudes, which look more white. 

This colour variation is thought to be due to differences in ice grain size in the two locations. Images taken through near-infrared, green and violet filters have been combined to produce this view. 

The images have been corrected for light scattered outside of the image, to provide a color correction that is calibrated by wavelength. 

Gaps in the images have been filled with simulated color based on the colour of nearby surface areas with similar terrain types. 

This global colour view consists of images acquired by the Galileo Solid-State Imaging (SSI) experiment on the spacecraft's first and fourteenth orbits through the Jupiter system, in 1995 and 1998, respectively.

Image scale is 2 miles (1.6 kilometers) per pixel. North on Europa is at right. 

Credit: NASA/JPL-Caltech/SETI Institute

SISSA: Simple, like a neutron star

For astrophysicists neutron stars are extremely complex astronomical objects.

Research conducted with the collaboration of SISSA and published in the journal Physical Review Letters demonstrates that in certain respects these stars can instead be described very simply and that they show similarities with black holes.

In how many ways can one describe an object?

Take an apple: by just looking at it we can easily estimate its weight, shape and colour but we are unable to describe it at any other level, for example, to evaluate the chemical composition of its flesh.

Something similar also applies to astronomical objects: until today one of the challenges facing scientists was to describe neutron stars at the nuclear physics level.

The matter these stars are made up of is in fact extremely complex, and several complicated equations of state have been proposed.

However, to date there is no agreement as to which is the correct (or the best) one.

A theoretical study conducted by SISSA (the International School for Advanced Studies of Trieste), in collaboration with Athens University, has demonstrated that neutron stars can also be described in relatively simple terms, by observing the structure of the space-time surrounding them.

"Neutron stars are complex objects owing to the matter that composes them. We can picture them as enormous atomic nuclei with a radius of about ten kilometres", explains Georgios Pappas, first author of the study carried out at SISSA.

"A neutron star is what remains of the collapse of a massive star: the matter inside it is extremely dense and mostly consisting of neutrons".

"The nuclear physics required to understand the nature of the matter contained in these astronomical objects generally makes their description very complicated and difficult to formulate," continues Pappas.

"What we have demonstrated, by using numerical methods, is that there are properties that can provide a description of some aspects of neutron stars and the surrounding space-time in a simple manner, similar to the description used for black holes".

Black holes are truly unique objects: they have lost all matter and are only made up of space and time. Just like neutron stars they are the result of the collapse of a bigger star (in this case much bigger than the stars giving rise to neutron stars) and in the implosion all the matter has been swept away.

"They are considered to be the most perfect objects in the Universe and the expression 'hairless' that was coined by John Archibald Wheeler to indicate their simplicity has become famous. According to our calculations even neutron stars can be depicted in a very similar manner".

More Information: 'Effectively universal behaviour of rotating neutron stars in general relativity makes them even simpler than their Newtonian counterparts' Authors: George Pappas and Theocharis A. Apostolatos - Phys. Rev. Lett.

Black Holes Have Simple Feeding Habits

At the centre of spiral galaxy M81 is a supermassive black hole about 70 million times more massive than our sun.

Image Credit: X-ray: NASA /CXC /Wisconsin /D.Pooley & CfA /A.Zezas; Optical: NASA /ESA /CfA /A.Zezas; UV: NASA /JPL-Caltech /CfA /J.Huchra et al.; IR: NASA /JPL-Caltech /CfA

Dark Matter: Can Simple Anapole theory explain it?

This is a comparison of an anapole field with common electric and magnetic dipoles. The anapole field, top, is generated by a toroidal electrical current. 

As a result, the field is confined within the torus, instead of spreading out like the fields generated by conventional electric and magnetic dipoles. 

Credit: Michael Smeltzer, Vanderbilt University

Most of the matter in the universe may be made out of particles that possess an unusual, donut-shaped electromagnetic field called an anapole.

This proposal, which endows dark matter particles with a rare form of electromagnetism, has been strengthened by a detailed analysis performed by a pair of theoretical physicists at Vanderbilt University: Professor Robert Scherrer and post-doctoral fellow Chiu Man Ho.

An article about the research was published online last month by the journal Physics Letters B.

"There are a great many different theories about the nature of dark matter. What I like about this theory is its simplicity, uniqueness and the fact that it can be tested," said Scherrer.

Robert Scherrer

In the article, titled "Anapole Dark Matter," the physicists propose that dark matter, an invisible form of matter that makes up 85 percent of the all the matter in the universe, may be made out of a type of basic particle called the Majorana fermion.

The particle's existence was predicted in the 1930's but has stubbornly resisted detection.

A number of physicists have suggested that dark matter is made from Majorana particles, but Scherrer and Ho have performed detailed calculations that demonstrate that these particles are uniquely suited to possess a rare, doughnut-shaped type of electromagnetic field called an anapole.

This field gives them properties that differ from those of particles that possess the more common fields possessing two poles (north and south, positive and negative) and explains why they are so difficult to detect.

"Most models for dark matter assume that it interacts through exotic forces that we do not encounter in everyday life. Anapole dark matter makes use of ordinary electromagnetism that you learned about in school – the same force that makes magnets stick to your refrigerator or makes a balloon rubbed on your hair stick to the ceiling," said Scherrer.

"Further, the model makes very specific predictions about the rate at which it should show up in the vast dark matter detectors that are buried underground all over the world. These predictions show that soon the existence of anapole dark matter should either be discovered or ruled out by these experiments."

More information: Anapole dark matter. Physics Letters B, 2013; 722 (4-5): 341 DOI: 10.1016/j.physletb.2013.04.039 ( adsabs.harvard.edu/abs/2013PhLB..722..341)