Mars probe makes 'ice discovery'

Tiny clumps of material in the bottom left of the trench on 15 June (left) are gone by 19 June (right) Enlarge Image

Nasa's Phoenix lander has unearthed compelling evidence of ice on Mars, mission scientists believe.

Chunks of a bright material found in a trench dug by the craft have disappeared over four Martian days, suggesting they have vapourised.

While digging in another trench, the lander's arm connected with a hard surface at the same depth.

The finds lend weight to suggestions water is locked up in a permafrost layer close to the planet's surface.

Missing matter

"It must be ice,"

said Dr Peter Smith, Phoenix's principal investigator, who is based at the University of Arizona, Tucson.

"These little clumps completely disappearing over the course of a few days, that is perfect evidence that it's ice," he said.

"There had been some question whether the bright material was salt," he added.

"Salt can't do that."

The dice-sized chunks were unearthed in a trench informally known as Dodo-Goldilocks, which Phoenix dug and photographed on the 20th day of its stay on Mars.

Four days later when the trench was snapped again, some of the chunks had disappeared.

Earlier in the mission hopes of discovering ice were fading as soil samples scooped up earlier by Phoenix yielded no trace of water.

While evidence of ice on Mars has been gathered before, part of Phoenix's mission is to search out evidence to support the idea that the polar region of the planet could be habitable.

'Same depth'

Further confirmation of the ice theory came from another trench, known as Snow White 2.

Digging there was halted when the scraper on the lander's robotic arm hit a hard surface just under the soil layer.

"We have dug a trench and uncovered a hard layer at the same depth as the ice layer in our other trench," said Ray Arvidson of Washington University in St Louis, who is lead scientist for the robotic arm.

The arm also stopped three times earlier while digging in a "polygon".

This automatic reaction is a programmed response triggered when the scoop hits a hard, sub-surface region.

"Polygons" are soil features seen on Earth when permafrost layers in soil expand and contract as temperatures rise and fall.

Phoenix now seems to have confirmed that similar features on Mars are caused by the same processes as those on this planet.

Trio of 'super-Earths' discovered

The planets are rocky worlds between two and 10 times the size of Earth

Astronomers have identified a trio of so-called "super-Earths" - rocky planets between two and 10 times the mass of Earth.

The three new planets were detected using the Harps instrument at the La Silla Observatory in central Chile.

The star they circle is slightly smaller than our Sun, and is located 42 light-years away near the southern Doradus and Pictor constellations.

The discoveries were announced at an astronomy conference in Nantes, France.

When a planet orbits its star, it exerts a gravitational pull which causes the parent star to "wobble" around its centre of mass.

The High Accuracy Radial velocity Planet Searcher (Harps) spectrograph was able to measure this wobble to a very high precision over a period of five years.

This was vital because the perturbations caused by the planets were tiny.

"The mass of the smallest planet is one hundred thousand times smaller than that of the star," said co-author Francois Bouchy, from the Astrophysics Institute of Paris, France.

Chances are

The new worlds, which circle the star HD 40307, are 4.2, 6.7 and 9.4 times the size of Earth. They are named super-Earths because they are more massive than the Earth but less massive than Uranus and Neptune (which are about 15 Earth masses).

Using Harps data, the astronomers also counted a total of 45 candidate planets with a mass below 30 Earth masses.

This implies that one solar-like star out of three harbours such planets.

Astronomer Michel Mayor from the Geneva Observatory in Switzerland commented: "Does every single star harbour planets and, if yes, how many?

"We may not yet know the answer but we are making huge progress towards it."

Since the discovery in 1995 of a planet around the star 51 Pegasi by Michel Mayor and his colleague Didier Queloz, more than 270 exoplanets have been found - mostly around Sun-like stars.

The majority of these planets are gas giants, a bit like Jupiter or Saturn in our own Solar System. Current data shows that about one in 14 stars harbours this kind of planet.

The Harps instrument is attached to the La Silla 3.6m telescope in Chile. The facility is run by the European Southern Observatory (Eso) organisation.

Scientists confirm that parts of earliest genetic material may have come from the stars

by Eurek Alert

Thanks to Richard Prins for the link.

http://www.eurekalert.org/pub_releases/2008-06/icl-sct061308.php

Scientists confirm that parts of earliest genetic material may have come from the stars

Scientists have confirmed for the first time that an important component of early genetic material which has been found in meteorite fragments is extraterrestrial in origin, in a paper published on June 15, 2008

The finding suggests that parts of the raw materials to make the first molecules of DNA and RNA may have come from the stars.

The scientists, from Europe and the USA, say that their research, published in the journal Earth and Planetary Science Letters, provides evidence that life's raw materials came from sources beyond the Earth.

The materials they have found include the molecules uracil and xanthine, which are precursors to the molecules that make up DNA and RNA, and are known as nucleobases.

The team discovered the molecules in rock fragments of the Murchison meteorite, which crashed in Australia in 1969.

They tested the meteorite material to determine whether the molecules came from the solar system or were a result of contamination when the meteorite landed on Earth.

The analysis shows that the nucleobases contain a heavy form of carbon which could only have been formed in space. Materials formed on Earth consist of a lighter variety of carbon.

Lead author Dr Zita Martins, of the Department of Earth Science and Engineering at Imperial College London, says that the research may provide another piece of evidence explaining the evolution of early life. She says:

"We believe early life may have adopted nucleobases from meteoritic fragments for use in genetic coding which enabled them to pass on their successful features to subsequent generations."

Between 3.8 to 4.5 billion years ago large numbers of rocks similar to the Murchison meteorite rained down on Earth at the time when primitive life was forming. The heavy bombardment would have dropped large amounts of meteorite material to the surface on planets like Earth and Mars.

Co-author Professor Mark Sephton, also of Imperial's Department of Earth Science and Engineering, believes this research is an important step in understanding how early life might have evolved. He added:

"Because meteorites represent left over materials from the formation of the solar system, the key components for life -- including nucleobases -- could be widespread in the cosmos. As more and more of life's raw materials are discovered in objects from space, the possibility of life springing forth wherever the right chemistry is present becomes more likely."

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For further information please contact:

Colin Smith
Press Officer
Imperial College London
Email: cd.smith@imperial.ac.uk
Tel: +44 (0)207 594 6712
Out of hours duty press officer: +44 (0)7803 886 248

Dr Zita Martins
Department of Earth Science and Engineering
South Kensington Campus
Imperial College London
London SW7 2AZ, UK
Tel: +44 (0)20 7594 9982
Fax: +44 (0)20 7594 7444
Email: z.martins@imperial.ac.uk
http://www.imperial.ac.uk/people/z.martins

Notes to editors:

1. "Extraterrestrial nucleobases in the Murchison meteorite", Earth and Planetary Science Letters, Sunday 15 June 2008 (Print publication)

A full copy of the research can be downloaded at: http://dx.doi.org/10.1016/j.epsl.2008.03.026