Searching for the 'real' waterworld

July 09, 2003

At the recent ESA co-sponsored 'Towards Other Earths' conference, nearly 250 of the world's leading experts in planet detection discussed the strategy for finding Earth-like worlds. Alain Léger and colleagues of the Institut d'Astrophysique Spatiale, France, described a new class of planets that could be awaiting discovery: 'waterworlds'.

According to Léger and his colleagues, these waterworlds would contain about six times the mass of Earth, in a sphere twice as wide as our planet. They would possess atmospheres and orbit their parent star at roughly the same distance that the Earth is from the Sun. Most excitingly, an ocean of water entirely covers each world and extends over 25 times deeper than the average depth of the oceans on Earth.

A hundred kilometres deep

According to calculations, the internal structure of a waterworld would consist of a metallic core with a radius of about 4000 kilometres. Then there would be a rocky mantle region extending to a height of 3500 kilometres above the core's surface, covered by a second mantle made of ice up to 5000 kilometres thick. Finally, an ocean blankets the entire world to a depth of 100 kilometres, with an atmosphere on top of this.

With twice the radius of the Earth, they will be easily spotted by the Eddington spacecraft, which is designed to detect planets down to half the size of the Earth. "A waterworld passing in front of a star, somewhat cooler than the Sun, will cause a dimming in the stellar light by almost one part in a thousand. That's almost ten times larger than the smallest variation Eddington is designed to detect. So, waterworlds - if they exist - will be a very easy catch for Eddington," says Fabio Favata, ESA's Eddington Project Scientist.

The CNES/ESA mission Corot, which is a smaller, precursor mission to Eddington due for launch around 2005, may also be just able to glimpse them, if they are close enough to their parent stars.

Origins of life

Scientists are now asking if such worlds could support life, and what would it be like, especially since water is a prime ingredient for life on Earth. While waterworlds seem to have everything to sustain life, there is a big question mark over whether they could actually allow it to start in the first place.

One of the leading theories for life's origin in deep oceans is that it requires hot springs on the ocean floor, heated by volcanic activity like the 'black smokers' found here on Earth. On a waterworld however, 5000 kilometres of ice separate the ocean floor from any possible smokers. On the other hand, a water-surface origin may still be possible.

Perhaps the only way to know if anything lives on a waterworld will be to study them with ESA's habitable-planet-finding mission, Darwin. When it launches in around 2014, this flotilla of spacecraft will look for tell-tale signs of life in the atmospheres of any planets, including waterworlds.
-end-


European Space Agency

Related Planets Articles from Brightsurf:

Stars and planets grow up together as siblings
ALMA shows rings around the still-growing proto-star IRS 63

Two planets around a red dwarf
The 'SAINT-EX' Observatory, led by scientists from the National Centre of Competence in Research NCCR PlanetS of the University of Bern and the University of Geneva, has detected two exoplanets orbiting the star TOI-1266.

Some planets may be better for life than Earth
Researchers have identified two dozen planets outside our solar system that may have conditions more suitable for life than our own.

Fifty new planets confirmed in machine learning first
Fifty potential planets have had their existence confirmed by a new machine learning algorithm developed by University of Warwick scientists.

Rogue planets could outnumber the stars
An upcoming NASA mission could find that there are more rogue planets - planets that float in space without orbiting a sun - than there are stars in the Milky Way, a new study theorizes.

Could mini-Neptunes be irradiated ocean planets?
Many exoplanets known today are ''super-Earths'', with a radius 1.3 times that of Earth, and ''mini-Neptunes'', with 2.4 Earth radii.

As many as six billion Earth-like planets in our galaxy, according to new estimates
There may be as many as one Earth-like planet for every five Sun-like stars in the Milky way Galaxy, according to new estimates by University of British Columbia astronomers using data from NASA's Kepler mission.

How planets may form after dust sticks together
Scientists may have figured out how dust particles can stick together to form planets, according to a Rutgers co-authored study that may also help to improve industrial processes.

Planets around a black hole?
Theoreticians in two different fields defied the common knowledge that planets orbit stars like the Sun.

The rare molecule weighing in on the birth of planets
Astronomers using one of the most advanced radio telescopes have discovered a rare molecule in the dust and gas disc around a young star -- and it may provide an answer to one of the conundrums facing astronomers.

Read More: Planets News and Planets Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.