Earth and its moon seen as doted beacons from distant Space

Earth as bigger dot and the moon as the smaller

NASA has released pictures of the Earth and its moon taken by a distant spacecraft. Images taken, on July 19 show our planet and its moon as bright beacons from millions of miles away in space.

Colored images were captured by NASA's Cassini spacecraft from its perch in the Saturn system nearly 900 million miles (1.5 billion kilometers) away. MESSENGER, the first probe to orbit Mercury on the other hand, is said to have taken a black-and-white image from a distance of 61 million miles (98 million kilometers) as part of a campaign to search for natural satellites of the planet.

In the Cassini images Earth and the moon can be seen as mere dots. According to NASA this was the first time Cassini's highest-resolution camera captured Earth and its moon as two distinct objects. The latest pictures really show how colossal the distance between planets can be.

NASA invited the public to celebrate the event by finding Saturn in their part of the sky, waving at the ringed planet and sharing pictures over the Internet. Thousands around the world participated.

"We can't see individual continents or people in this portrait of Earth, but this pale blue dot is a succinct summary of who we were on July 19," said Linda Spilker, Cassini project scientist, at NASA's Jet Propulsion Laboratory (JPL) in Pasadena, Calif.

"Cassini's picture reminds us how tiny our home planet is in the vastness of space, and also testifies to the ingenuity of the citizens of this tiny planet to send a robotic spacecraft so far away from home to study Saturn and take a look-back photo of Earth."

It is very rare to catch pictures of the earth from the outer solar system as from that distance, Earth appears very close to our sun and not easily discerned. This is also because a camera's sensitive detectors can be damaged by looking directly at the sun, just as a human being can damage his or her retina by doing the same. Cassini was able to take this image because the sun had momentarily moved behind Saturn from the spacecraft's point of view and most of the light was blocked.

"It thrills me to know that people all over the world took a break from their normal activities to go outside and celebrate the interplanetary salute between robot and maker that these images represent," said Carolyn Porco, Cassini imaging team lead at the Space Science Institute in Boulder, Colo. "The whole event underscores for me our 'coming of age' as planetary explorers."

Principal investigator Sean Solomon of Columbia University revered their efforts boasting that “images of our planet have been acquired on a single day from two distant solar system outposts reminds us of this nation's stunning technical accomplishments in planetary exploration". "And because Mercury and Saturn are such different outcomes of planetary formation and evolution, these two images also highlight what is special about Earth. There's no place like home."

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New model for the make-up of the earth unearthed.

The study may explain a longstanding puzzle about the most inaccessible part of our planet. A novel model has been put up to explain the nature of earth core. This follows a discovery that the core is hotter than ordinary fire. The theory proposes that observed differences between the east and west hemispheres of the core are explained by the arrangement of iron atoms. Details of the study are found at nature.com journal Scientific Reports.


According to the study, Lying more than 5,000 km beneath our feet, at the centre of the Earth, the core is beyond the reach of direct investigation. Broadly speaking, it consists of a solid sphere of metal sitting within a liquid outer core. It is assumed that the inner core started to solidify more than a billion years ago. The core has a radius of about 1,220 km which grows by about 0.5 mm each year.
The substance that consist the core remains a longstanding unresolved conundrum. However, scientists suggest that we can get clues come from the speeds that seismic waves generated by earthquakes pass through the core. These tell its density and elasticity. The two characteristics also depend on the precise arrangement of iron atoms forming the crystalline core. The precise arrangement of the iron atoms however, still remains unclear, since the conditions of extreme pressure and temperature at the core cannot easily be replicated in the laboratory.

Available seismic data indicate that the western and eastern hemispheres of Earth's inner core differ, and this has led some to suggest that the core was once subjected to an impulse - presumably from the collision of a space rock or planetoid which shook the whole Earth.

The core is suggested to constantly be moving sideways. As it does, the front side is melting and the rear side crystallizing, but the core is held centrally by gravity. With all these seismic complexities, the link between the crystal structure and the geophysical observations has yet to be resolved.

Scientists including; Maurizio Mattesini from the Complutense University of Madrid, Spain, and colleagues propose a novel possibility for the structure of the core: that it is composed of mixtures of different iron arrangements distinguished by the way their atoms pack together. By comparing seismic data from over one thousand earthquakes across the globe with quantum mechanical models for the properties of iron, they suggest that seismic variations directly reflect variations in the iron structure.

They propose that the eastern and western sides of the core differ in the extent of mixing of these distinct structures, and suggest their results account for the dynamic eastward drift of the core through time. Their robust but intricate picture of the core sharply contrasts with earlier suggestions of a more uniform mineralogy. One likely limitation of the model is the assumption that the iron core is pure without any impurities and alloys.

Dr Arwen Deuss, a renowned seismologist from the University of Cambridge, commented that the model is a step in the right direction, directly comparing seismology with mineral physical properties. She added that the move should eventually provide a better understanding of the birth and evolution of our planet.

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