Surreal Sunrise

Clouds flow like a river over the lights of Swiss villages as the rising sun crowns the Alps with morning gold in a January 30 picture. To the right, a crescent moon and the bright dot of Venus decorate the paling sky.

Venus is closer to the sun than Earth, so—like a car going around a racetrack—Venus periodically overtakes Earth as it orbits. This means Venus changes from the evening star, visible after sunset, to the morning star, visible before sunrise, every 584 days.

Star-Struck Aurora

Stars wheeling across the sky seem to cut through a fiery aurora in a recently released long-exposure picture taken in western Sweden.

Auroras can appear in different colors depending on the types of gases in the atmosphere and where these gases are. Auroras happen when energized particles form the sun interact with air molecules and give them extra charge. These “excited” molecules then emit light. Oxygen, for example, can create auroras in yellow-green to red, while nitrogen emits light in blues and purples.

Aft View of Earth

An astronaut aboard the International Space Station snapped this recently released shot of the station’s rear end with Earth in the distance from aboard the ISS Progress 40 supply vehicle.

The unpiloted Progress 40 craft has since undocked from the station carrying waste items. The craft will be used for scientific experiments until it is burned up in Earth’s atmosphere.

Double Trouble

An arch of plasma called a solar filament erupts from the sun on January 28 in a video still from NASA’s Solar Dynamics Observatory spacecraft.

The craft caught the sun producing two events at once: At the same time the filament erupted, a coronal mass ejection on the opposite side of the solar disk (not pictured) blasted a huge spray of particles into space.

Have a Nice Day?

People with coulrophobia might want to avoid the south pole of Mars: Seasonal carbon dioxide frost has given rise to a pit that bears an eerie resemblance to a deranged clown face.

Scientists compared this newly released picture from the Mars Reconnaissance Orbiter with another taken in 2007 to see how the pit has changed over time. The team saw signs of growth inside the “happy face,” which they think is caused by frost that sublimates—turns directly from solid to gas—from the pit walls and then recondenses on its surfaces.

Snowy Berlin

Bright white snow and dark vegetation create a crystalline patchwork over the urban landscape of Berlin in a recently released satellite image of the German capital. Home to 3.4 million people, Berlin has the second largest population, within city limits, of any city in the European Union after London.

The picture was taken by the Japanese ALOS satellite and processed by theEuropean Space Agency. ALOS was designed to chart land cover in visible and near-infrared light.

WISE Comets

After a year of mapping the sky in infrared, NASA’s Wide-field Infrared Survey Explorer, or WISE, space telescope discovered 20 comets, seen above in a mosaic of false-color pictures. The backgrounds appear fuzzy because WISE also captured the faint heat signatures of dust in our solar system.

In addition to comets, WISE discovered more than 33,000 asteroids in the main belt, between the orbits of Mars and Jupiter, and 134 near-Earth objects—asteroids and comets that come within 28 million miles (45 million kilometers) of Earth’s orbit around the sun.

New research has settled decades of scientific debate about a puzzling aspect of space weather. Researchers from the University of California (UCLA) and British Antarctic Survey (BAS) have found the final link between electrons trapped in space and the glow of light from the upper atmosphere known as the diffuse aurora.

The research, published in the latest issue of the journal Nature, promises to further understanding of space weather, with benefits for the satellite, power grid and aviation industries, and how space storms affect the Earth’s atmosphere from the top down.

Scientists have long understood that the ‘diffuse aurora’ is caused by electrons striking the upper atmosphere. However, the electrons are normally trapped much higher up in the Earth’s magnetic field through a long chain of events starting with the Sun. The problem is to understand how these electrons reach the atmosphere.

Since the 1970s scientists have debated whether very low frequency (VLF) radio waves could scatter the trapped electrons into the atmosphere. Two types of VLF waves were identified in space as the possible cause of the ‘diffuse aurora’, but despite years of argument and research no conclusive result had been possible. The new research shows, without doubt, that VLF waves known as ‘chorus’ are responsible; so-called since the signals detected by ground-based recording equipment sound like the bird’s dawn chorus when played back through a loud speaker.

Through detailed analysis of satellite data the authors were able to calculate the effects on the trapped electrons and identify which radio waves were causing the scattering.

Lead author Professor Richard Thorne from UCLA says: "The breakthrough came when we realised that the electrons being lost from space to the Earth’s atmosphere were leaving a signature, effectively telling a story about how they were being scattered. We could then analyse our satellite data on the two types of VLF waves and by running calculations on them — including the rate at which the electrons were being lost to the Earth’s atmosphere — we could clearly see that chorus waves were the cause of the scattering."

Professor Richard Horne from British Antarctic Survey says: "Our finding is an important one because it will help scientists to understand how the diffuse aurora leads to changes in the chemistry of the Earth’s upper atmosphere, including effects on ozone at high altitude, which may affect temperature right through the atmosphere.

"We are also including the VLF waves into computer models to help predict ‘space weather’ which not only affects satellites and power grids, but also the accuracy of GPS navigation and high frequency radio communications with aircraft on polar routes."

The ‘diffuse aurora’, is not the same as the ‘discrete aurora’ known as the northern and southern lights. ‘Discrete aurora’ look like fiery moving curtains of colourful light and can be seen by the naked eye, whereas the diffuse aurora is much fainter but more extensive. The ‘diffuse aurora’, which typically accounts for three-quarters of the energy input into the upper atmosphere at night, varies according to the season and the 11 year solar cycle.

Notes:

*Chorus waves: Very low frequency radio waves coming from space and first detected on the ground. So-called because when played back through a loud speaker they sound like the bird’s dawn chorus.

*Diffuse aurora: caused when electrons that are trapped in the Earth’s magnetic field are funnelled towards the polar atmosphere. Light is emitted when the electrons collide with neutral atoms in the upper atmosphere. The diffuse aurora is not generally visible to the naked eye but is well captured in satellite images.

*Discrete aurora: known as the Aurora Borealis at the North Pole (above the Arctic circle) and Aurora Australis at the South Pole (above Antarctica). They look like fiery, moving curtains of colourful light and can be seen by the naked eye whereas the diffuse aurora is much fainter but is more extensive and can cover the whole sky.