Mars Had Liquid Water in Recent Past, Rover Finds

Even while snared in a sand trap, NASA's Mars rover Spirit has hit "wet" pay dirt: evidence of relatively recent groundwater activity on the red planet. For almost six months the rover has been precariously perched on the edge of a shallow crater in an equatorial region of Mars. The area is filled with cooled lava flows pitted by meteorite impacts.

While on a routine drive, Spirit broke through a thin crust of hard soil that capped a filled-in impact crater, and its wheels became half buried in the soft sand.

During one of these rescue attempts, Spirit churned up the soil and uncovered an intriguing layer of bright, fluffy soil. Mission managers had the rover take a closer look, and they discovered that the layer is in sulfates, minerals known to form on Earth only in the presence of liquid water.

Spirit and its twin rover Opportunity have discovered sulfate-rich soil in other regions of Mars before, said Ray Arvidson, a planetary scientist at the Washington University in St. Louis and a member of the rover science team.

But because most missions are scheduled in advance, the latest discovery marks the first time one of the robots has been stationary long enough to study sulfates in detail.

Snow on Mars

Spirit's data revealed that the newfound sulfates are likely evidence of past "wet eruptions" on Mars, when lava and sulfur-rich steam spewed from volcanic vents dotting the landscape billions of years ago.

But the crater contains a clue that liquid water continues to be active on Mars, at least in the long term: The soil is full of iron sulfate covered with a thin crust of calcium sulfate.

Sea urchins 'bulldozing' Tasmanian reef

A combination of overfishing and climate change are triggering catastrophic overgrazing of reefs by sea urchins in eastern Tasmania, say researchers.

Professor Craig Johnson of the University of Tasmania and colleagues report their findings today in the Proceedings of the National Academy of Sciences.

"When you get the two things happening together, it enables the urchin populations to build up to the point where they destructively graze," says Johnson.

Scientists believe climate change is causing stronger winds in the Southern Ocean, which speeds up the rotation of the ocean system that drives the East Australian Current.

The faster current has caused warmer water to spread further south, to the waters off eastern Tasmania, says Johnson.

He says this is causing the water in the area to warm nearly four times faster than the global average.

Northern invaders

The current is also carrying with it invaders from the north - the long-spined sea urchin (Centrostephanus rodgersii) from New South Wales waters.

"It is a really aggressive grazing species and it can just completely chew out the seaweeds and many of the other associated animals growing on the seafloor," says Johnson.

He says this can create a habitat called a "sea urchin barren".

"The analogy is like taking a bulldozer to a rainforest - you clear it back to bare earth," says Johnson.

"About 50% of the New South Wales coast looks like that right now."

Johnson says he and colleagues have previously found that the sea urchins are starting to form barrens in Tasmania and the race is on to stop these from spreading.

Research team member Dr Scott Ling also previously discovered that a key predator of the sea urchins is the spiny lobster (Jasus edwardsii), which is worth $50 million to the fishing industry.

The team's latest research looks at the impact on reefs of the interaction between climate change and the decline in the number of lobster predators due to overfishing.

Past decade set to be warmest on record

New research from the World Meteorological Organisation shows that the past decade has been the warmest since records began 160 years ago.

The United Nations weather agency and Britain's Met Office presented their findings at the Copenhagen climate change summit.

The figures show a steady rise in temperatures over the past four decades, with 2009 listed as likely to be the fifth warmest year since records began in 1850.

"In the last decade we have seen that the temperatures haven't gone up very much, but they are clearly a lot warmer then they were in the previous decade," says Dr Vicky Pope, head of climate change advice at the Met office.

Some of the UN's weather data was provided by Britain's University of East Anglia which is at the centre of a row over leaked emails which appear to suggest that the theories around man-made climate change are not solid.

The secretary-general of the WMO, Michel Jarraud, also observed that Australia has so far had its third warmest year on record.

"There were above-normal temperatures in most parts of the continents, and only in USA and Canada there were significant areas with cooler-than-average conditions," he says.

"But in large parts of Southern Asia, Central Africa, these regions are likely to have the warmest year on record."

Jarraud says the year has also been notable for extreme weather events.

"China with the third warmest year in the last 50 years, heat waves in Italy, UK, France, Belgium, Germany, an extreme heat wave in India, and Australia the third warmest year on record with three exceptional heat waves," he said.

Those heatwaves hit south-eastern Australia in January, February and November and the sub-tropical east in August.

Dark questions remain over dark energy

The recent discovery of a new kind of type 1A supernovae has raised fresh questions about their use in identifying the mysterious force known as dark energy.

Dubbed 'type point 1A' supernova, they are thought to be white dwarfs which have exploded at lower mass. They emit one-tenth the energy of other type 1A supernovae and have different chemical signatures.

It's an important discovery as all type 1A supernovae were previously thought to explode with similar mass and energy levels, allowing scientists to use them to measure distances in the universe.

Professor Brian Schmidt of the Research School of Astronomy and Astrophysics at the Australian National University in Canberra, has been investigating supernovae for more than a decade.

In 1998, he was part of a team that discovered the rate of the expansion of the universe was increasing by measuring the distance to supernovae events.

Schmidt says he realised "some force now called dark energy is causing space-time to expand at an ever accelerating rate".

'Biggest mistake'

Dark energy was first proposed by Albert Einstein, who like most scientists of his day, assumed the universe was stable.

His own equations showed that in such a universe, gravity would be the dominating force crushing everything together.

To counter this, Einstein 'invented' an expansion force to counter gravity, which he called the 'cosmological constant'.

When Edwin Hubble discovered a few decades later that the universe really was expanding, Einstein tore up his cosmological constant describing it as his greatest ever mistake.

So if type 1A supernovae aren't all the same can they still be trusted on issues as important as dark energy?

According to Schimdt, the answer is yes.

"Point 1A supernovae aren't an issue, because they're so much fainter, very rare, hard to find and only seen in nearby galaxies, making them different from usual type 1A supernovae".

The 'big rip'

A more extreme version of dark energy called 'phantom energy' could see forces increase so much, that it would lead to what some astronomers refer to as a 'big rip'.

The big rip would see the expansion of space-time occur not just on the cosmic scale of relativity theory, but on the subatomic scale of quantum mechanics.

It would tear apart atoms into protons, neutrons and electrons, even overcoming gluons to rip off quarks.

"For that to happen, dark energy needs to be created a little faster than space is created," says Schmidt. "As near as we can tell, both are created at exactly the same rate."

"Still if it did happen a hundred billion years or so in the future, it would be dramatic and quick, the stars would go out in the sky and minutes later we would be ripped to shreds.'