24Feb2012

Alien Aurora Can Be Stunningly Beautiful

Aurora on Earth are stunning to watch, but have you ever wondered what they might look like on other planets? We took a journey to some alien worlds to find out what auroras look like there. There is no doubt that extraterrestrial auroras can be very beautiful on other places in the Universe, and sometimes this light show can be very unique.

On Earth, an aurora is created when atoms in solar plasma interacts with atoms in Earth’s upper atmosphere. In our solar system, there are many bodies that generate a substantial magnetic field. So you could see an aurora on Mercury, Earth, Jupiter, Saturn, Uranus, and Neptune, but it would not be possible on Venus, the Earth’s moon, comets, and asteroids.

In 2010, the Cassini spacecraft observed Saturn’s radio aurora. It turned out that there were some similarities and some contrasts between the radio auroral emissions generated at Saturn and those at Earth.     Earth also has radio auroral emissions and results showed that the process that generates radio aurora appears to be the same at both planets.

Interestingly, there are two minor differences between the aurora at Earth and Saturn. At Earth, there is a cavity in the plasma above the auroral oval that rises for several thousand kilometres. Observations showed that this is not seen at Saturn.

Secondly, radio sources were crossed at much further distances from the planet. Cassini detected not only unusually strong electric currents, but it also provided scientists with evidence of an active aurora.

“We think that the unusual conditions responsible for these intense electric currents might have been triggered by a solar wind compression squeezing Saturn’s magnetic field and producing the observed auroras,” said Emma Bunce, a team member from the University of Leicester in the UK.

Image of Saturn's aurora seen at ultraviolet wavelengths. The spiral shape seen here is similar to the distorted radio aurora visualised by the team and also indicates enhanced auroral activity. (Credit: ESA/NASA/Hubble)

Though the aurora resembles the same phenomenon that crowns Earth’s polar regions, the Hubble image shows unique emissions from the magnetic “footprints” of three of Jupiter’s largest moons.

Auroral footprints can be seen in this image from Io (along the lefthand limb), Ganymede (near the center), and Europa (just below and to the right of Ganymede’s auroral footprint). These emissions, produced by electric currents generated by the satellites, flow along Jupiter’s magnetic field, bouncing in and out of the upper atmosphere. They are unlike anything seen on Earth.

To see an aurora on Jupiter is not a unique event. Jupiter has a permanent ring of auroral light surrounding each of its poles. it has long been believed that the light originates from Io, but new research suggest the Sun also plays a vital role in creating the lights.

Io can control Jupiter’s auroras over long timescales, but “this does not rule out contributions from the solar wind,” says Margaret Kivelson of the University of California, Los Angeles. Although a lot is known about the blue light, there are still some mysteries to be solved. Scientists must attempt to find out how the charged particles are accelerated along Jupiter’s magnetic field lines. This can hopefully be accomplished when Juno spacecraft reaches Jupiter in 2016.

The most remarkable magnetosphere in the solar system was found by Voyager 2 in its encounter with Uranus. This aurora was found at the feet of magnetic field lines threading only the tail side of the middle magnetosphere, as though it were excited by connection to a partial ring current, and was apparently co-located with the sources of whistler-mode plasma waves and some types of kilometric radio waves (UKR) also observed by Voyager at Uranus.

Mars as seen by the Hubble Space Telescope

To see an aurora on Mars is a unique experience, but some years ago, using the ultraviolet spectrometer (SPICAM) on board the Mars Express satellite, Jean-Loup Bertaux of the Service d’Aeronomie du CNRS in France and his colleagues observed a Martian aurora.

Unlike the other large planets’ celestial shows, which occur near the poles, the light show above the Red Planet manifests around areas of magnetized rock in the planet’s crust.

“Mars has no internally generated, planetary-scale magnetic field,” explains Bill Sandel of the University of Arizona. “It has what are called ‘crustal magnetic anomalies’ scattered around the Martian surface, remnants of what presumably was Mars’s planetary-scale magnetic field that was active when the planet was younger.”

The aurora measured some 30 kilometers across and appeared about 130 kilometers above the surface. It corresponds to a distinct type of aurora not seen before in the solar system.

For the time being nothing can be said about Pluto. Whether it is possible or not to see an aurora on Pluto remains still a mystery. Source: Message To Eagle

Related articles

 

 Amazing Red Aurora Over Australia

This fantastic red aurora over the Mornington peninsula in Australia was captured by Alex Cherney, an amateur astronomer who after chasing it for more than two years was finally rewarded with two displays of Aurora Australis (Southern lights) within a week.

“The nights were warm an clear and the Moon was not in the sky either – I could not have asked for better conditions. The red color of this aurora is caused by the charged particles from the Sun exciting oxygen atoms high in the Earth’s atmosphere. Hopefully there will be more to come as Sun’s activity increases in 2012-13.

Being able to photograph it all night I came up with a nice video. The brighter Aurora happened on January 22nd and the smaller one, featured in the middle section, was from January 16th, followed by a rather bright Moonrise, ” writes Alex on his blog Terrastro  Source: Message To Eagle