With voices hardly louder than an insect's buzz, the tiniest frogs ever discovered are smaller than a coin and hop about the rainforest of the tropical island of Papua New Guinea, US scientists said Wednesday.

Not only are these little peepers with the big names -- Paedophryne amauensis and Paedophryne swiftorum -- the smallest frogs known to man, they are also believed to be the smallest vertebrates on Earth, said the report in the science journal PLoS ONE.

Until now the smallest vertebrate was believed to be a transparent Indonesian fish known as Paedocypris progenetica that averaged about eight millimeters (one-third inch).

The largest vertebrate is the blue whale, measuring about 25.8 meters (yards).

The little land frog Paedophryne amauensis comes in at a whopping 7.7 millimeters, or less than one-third of an inch. The other newly discovered kind, Paedophryne swiftorum, measures a bit over eight millimeters.

Internet addiction has for the first time been linked with changes in the brain similar to those seen in people addicted to alcohol, cocaine and cannabis. In a groundbreaking study, researchers used MRI scanners to reveal abnormalities in the brains of adolescents who spent many hours on the internet, to the detriment of their social and personal lives. The finding could throw light on other behavioural problems and lead to the development of new approaches to treatment, researchers said.

An estimated 5 to 10 per cent of internet users are thought to be addicted - meaning they are unable to control their use. The majority are games players who become so absorbed in the activity they go without food or drink for long periods and their education, work and relationships suffer.

Henrietta Bowden Jones, consultant psychiatrist at Imperial College, London, who runs Britain's only NHS clinic for internet addicts and problem gamblers, said: "The majority of people we see with serious internet addiction are gamers - people who spend long hours in roles in various games that cause them to disregard their obligations. I have seen people who stopped attending university lectures, failed their degrees or their marriages broke down because they were unable to emotionally connect with anything outside the game."

In November 2011, NASA launched its biggest, most ambitious mission to Mars. The $2.5 billion Mars Science Lab spacecraft will arrive in orbit around the Red Planet this August, releasing a lander that will use rockets to control a slow descent into the atmosphere. Equipped with a "sky crane," the lander will gently lower the one-ton Curosity rover on the surface of Mars. Curiosity, which weighs five times more than any previous Martian rover, will perform an unprecedented battery of tests for three months as it scoops up soil from the floor of the 96-mile-wide Gale Crater. Its mission, NASA says, will be to "assess whether Mars ever was, or is still today, an environment able to support microbial life."

For all the spectacular engineering that's gone into Curiosity, however, its goal is actually quite modest. When NASA says it wants to find out if Mars was ever suitable for life, they use a very circumscribed version of the word. They are looking for signs of liquid water, which all living things on Earth need. They are looking for organic carbon, which life on Earth produces and, in some cases, can feed on to survive. In other words, they're looking on Mars for the sorts of conditions that support life on Earth.

But there's no good reason to assume that all life has to be like the life we're familiar with. In 2007, a board of scientists appointed by the National Academies of Science decided they couldn't rule out the possibility that life might be able to exist without water or carbon. If such weird life on Mars exists, Curiosity will probably miss it.

Last year, using the exoplanets discovered by the Kepler space telescope as a guide, astronomers took a statistical stab at estimating the number of exoplanets that exist in our galaxy. They came up with at least 50 billion alien worlds.

Today, astronomers from the Space Telescope Science Institute (STScI) in Baltimore, Md., and the PLANET (Probing Lensing Anomalies NETwork) collaboration have taken their own stab at the "galactic exoplanetary estimate" and think there are at least 100 billion worlds knocking around the Milky Way.

Why has the estimate doubled? The key difference here are the methods used to detect alien worlds orbiting distant stars.

The Kepler space telescope watches the same patch of sky -- containing around 100,000 stars -- and waits for slight "dips" in starlight brightness. This dip occurs when an exoplanet passes in front of its parent star, thereby blocking a tiny fraction of light from view.

A new index assessing the vulnerability of the world's stocks of weapons-grade nuclear material produces some surprising results.

The Nuclear Threat Initiative, a respected non-proliferation think tank, and the Economic Intelligence Unit have produced a new ranking system to assess the security of the world's scattered stocks of weapons-grade uranium and plutonium.

The NTI Nuclear Materials Security Index is meant to be a measure of how vulnerable those stocks are to theft by terrorists or criminal groups. It is also intended to provide a baseline for assessing progress in locking those stockpiles up, ahead of the next Nuclear Security Summit, due in Seoul at the end of March.

The authors insist this is about establishing an objective view of the work still to be done to meet Barack Obama's ambitious goal to secure the global stockpiles by 2014. This is not about "naming and shaming" they insist. But if you publish a list comparisons are going to be made.

New "Eco-Bulbs" originally scheduled to become mandatory January 1, 2012 have been pushed back to October. On the horizon however are "Bio-Bulbs"

As late-night workers and long-distance travelers already know, shifting time zones or work periods throws the body's natural clock out of whack.

Even regular folks often find it nearly impossible to get a restful sleep for several hours after sitting under bright lights after the sun has gone down (some call it the Fenway Park phenomena).

Now a Florida inventor is testing a new LED bio-bulb that could regulate the body's circadian rhythm by helping control the production of melatonin, the body's sleep hormone that tells us when it's nighttime.

A 47-million-year-old primate may have been a fashionista of sorts, as new analysis of the fossil suggests it sported grooming claws.

Besides helping the primate rake through its fur, particularly in hard-to-reach spots, the grooming claw presents a puzzle of sorts for scientists studying the relationship between a group that includes humans, apes and monkeys, and the family that includes lemurs.

That's because the primate is the first extinct North American primate with a toe bone showing features associated with the presence of both nails and a grooming claw.

Traditionally, it's thought that primates with a toe attachment called a grooming claw were more closely related to lemurs, which are primates like us but are considered more primitive and part of a different family than great apes (including humans) and monkeys. In lemurs, the claw is located on the second toe.

So where does this newly examined specimen fit in? It was "either in the process of evolving a nail and becoming more like humans, apes and monkeys, or in the process of evolving a more lemurlike claw," study researcher Doug Boyer, of Brooklyn College of New York, said in a statement.

Here in Austin, Texas, attendees at the American Astronomical Society meeting are buzzing about the discovery of a possible supernova in the irregular galaxy NGC 3239 by amateurs Bob Moore, Jack Newton, and Tim Puckett.

The supernova showed up in this unfiltered CCD image that the trio took during an automated observing run on January 7th with a 16-inch (40-cm) reflector in Portal, Arizona. At that time the putative supernova was at magnitude 14.6; Puckett confirmed it at 14.4 the next day with the same scope. The most recent value is 13.9, and it might continue to brighten before the explosion reaches its peak.

Several professional astronomers at the meeting have already started putting out e-mails and calls for spectroscopic observations. They hope to catch the supernova early and gain important information about what kind of explosion it is and, perhaps, what its progenitor was. Nothing shows up at this position in images taken by Puckett two weeks ago - at least, nothing brighter than magnitude 19.

When David Carroll wanted to find a way to make low-cost solar panels, he discovered he needed look no further than his own backyard.

In a weedy part of his Winston-Salem lot, pokeweed grows in wild, red-caned riot. Birds love the purple berries, and soon, so did Carroll. Because with pokeberries, the Wake Forest University scientist believes he's found a key to supplying electricity to parts of the developing world.

One Friday last year, Carroll, director of the Center for Nanotechnology and Molecular Materials at Wake Forest, was meeting with his students, brainstorming ways to get solar power to impoverished communities.

Traditional silicon solar panels are great, they agreed. But to make them, you need costly materials and a high-tech factory.

"We were sitting around thinking about the problem of how do you make it really, really cheap - and you can't get around the fact that (if you do), it's not going to be a very good solar cell. So it has to be very cheap to be worth it," Carroll recalled.

Natural dyes from plants rich in compounds called flavonoids can produce electrical current when sandwiched between the layers of a solar cell, in the spot where silicon would normally go.

The signs of aging show up in our genes as the protective caps on the ends of packets of our DNA, called chromosomes, gradually wear away over time.

Now, scientists have found that the length of these caps, called telomeres, measured early in life can predict life span.

Using 99 zebra finches, a small bird also popular as a pet, a team of researchers in the United Kingdom measured the lengths of the telomeres found in the birds' red blood cells over the course of their lives.

They found the length of the telomeres at the first measurement, made 25 days after the birds hatched, was the strongest predictor of how long the birds actually lived.

In addition, the birds with the longest telomeres early in life, and throughout the study, were the ones most likely to live into old age, up to 8.7 years old - a "ripe old age" for a finch, said study researcher Britt Heidinger, a postdoctoral researcher at the University of Glasgow.

For relatively long-lived vertebrates, such as zebra finches and humans, aging and telomere loss appear to go hand-in-hand. And while it seems reasonable that telomere length early on could predict life span in humans, too, it's not yet certain, since no similar study has been completed in humans, according to Heidinger.