Scanning the skies for Exoplanets and Exomoons in other solar systems

The best prospect for habitable exomoons may be around gas giants. 

Credit: NASA

The first exoplanet was discovered in 1994.

Twenty years later, NASA's exoplanet catalog lists more than 1700 planets confirmed around other stars.

Most of these extra-solar-systems have been measured by changes in light spectra, in stellar motion or dust disks around stars.

Some exoplanets-more than 40 as of today-have even been directly photographed.

Jupiter's moons

One way or the other, we know that exoplanets are out there in abundance, in places we thought they would be and in places we didn't dream a planet could possibly exist. So what comes next? Finding moons.

Exomoons are naturally formed satellites circling around planets in other solar systems. Like the exoplanets themselves, we assume that exomoons are out there in relatively high abundance.

This assumption is based partly upon what we see around us in our own Solar System and partly upon our hypotheses about planetary formation.

Saturn's moons

This is what we observe in our own Solar System: moons are extremely common.

From Earth's one Moon to Jupiter's (currently known) fifty, every planet in the Solar System one astronomical unit or more from the Sun has a natural satellite.

Even Pluto, no longer officially classified as a planet, has a smaller companion circling around it.

Of note, the solid bodies such as Earth and Pluto have very few companions, while gaseous bodies Jupiter, Saturn, Uranus and Neptune have many.

Pluto and Charon

Furthermore, the masses of the Moon and Charon have a very specific relationship to Earth and Pluto in terms of mass: each satellite is about 10-2 the mass of their parent planet.

By contrast, the ratio of satellite masses to parent planet masses for the gas giants is very different: 10-4.

The differences in mass-ratio, how massive the moon is compared to the parent planet, and the differences in composition between the moons of solid planets and those of the gas giants led to a search for different formation scenarios for Earth's moon and the moons of the outer planets.

This is the current hypothesis: that there are two different methods of satellite formation at work in our Solar System.

Amy Barr Mlinar

Both methods were recently reviewed by Dr.Amy Barr Mlinar of Brown University at the Space Telescope Science institute Spring Symposium.

"This has been worked out starting about in the 1960's up through now," said Barr, "You have this [moon/planet] mass ratio of about 10-2 for solid planets, and a [moon/planet] mass ratio of about 10-4 for planets with a gaseous envelope."

Essentially, difference in mass ratios reflects the two completely different origins of our Moon and the satellites of Jupiter.

At the high end of the moon/planet mass ratio, 10-2 are the satellites of solid bodies (Earth and Pluto). These moons were formed from collisions.

Sometime in the distant past an object some large percentage of Earth's size struck the Earth, knocking material away that later coalesced into the Moon. The same is likely true of Charon, Pluto's companion.

Read the full article here

ESA Mars Express: Searching for water near Tagus Valles

Craters once brim-full with sediments and water have long since drained dry, but traces of their former lives as muddy lakes cling on in the martian desert.

The images were taken on 15 January by ESA’s Mars Express, and feature a region just a few degrees south of the equator within the ancient southern highlands of Mars.

The unnamed region lies immediately to the north of an ancient riverbed known as Tagus Valles and east of Tinto Valles and Palos crater that were presented in an earlier release.

The 34 km-wide crater in the top left of the main images perhaps draws most attention with its chaotic interior.

Here, broad flat-topped blocks called mesas can be found alongside smaller parallel wind-blown features known as yardangs.

Both mesas and yardangs were carved from sediments that originally filled the crater, deposited there during a flood event that covered the entire scene.

Over time, the weakest sediments were eroded away, leaving the haphazard pattern of stronger blocks behind.

Further evidence of this crater’s watery past can be seen in the top right of the crater in the shape of a small, winding river channel.

Clues also hang onto the ghostly outline of an ancient crater some 20 km to the east (below in the main images).

While the crater has all but been erased from the geological record, a long meandering channel clearly remains, and flows towards the crater in the centre of the scene.

This central complex of craters is seen close up in the perspective view below, showing in more detail another channel-like feature, along with a highly deformed crater.

Perhaps the rim of this eroded crater was breached as sediments flooded the larger crater.

SETI and Three Piatcions: As Seen Through a Telescope

This is an interesting music video for Italian shoegaze band “Thee Piatcions“. Their Wall-Of-Sound, psychedelic music (they must be one of the loudest bands touring Europe) inspired us to create this sort of retro sci-fi comedy about searching for life in space and looking for love on Earth.