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UK's fast-track space mission to study exoplanet atmospheres

Kulvinder Singh, News reporter
Feb 6, 2015, 8:23 UTC

Sen—Within four years the UK could launch a mission that might peer into the atmospheres of extrasolar planets—planets that reside in solar systems other than our own—and tell us about their chemistry.

A workshop on the mission, called Twinkle, is being held today at the Royal Astronomical Society in London. In the future we could discover what sort of planets we should expect to possess nitrogen/oxygen atmospheres like Earth. Such planets are the likeliest candidates for life.

Twinkle, funded through a mix of private and public finance and led by University College London, also represents a rapid, cost-effective mission at £50 million. This is around a tenth the cost of comparable missions by international space agencies.

Largely this is due to innovations by Surrey Satellite Technology Ltd (SSTL) who are constructing Twinkle. These innovations have seen them become a successful manufacturer and exporter of satellites. The other factor is the use of off-the-shelf components.

Twinkle's operational life is three years, with the possibility of an extension of two years or more. It will analyse at least 100 exoplanets in the Milky Way.

When an exoplanet passes in front of its star, a sliver of starlight is filtered through the planet’s atmosphere. Twinkle will measure this light for a wide range of planet types—including rocky super-earths (1-10 times the mass of Earth) and hot-Jupiters (gas giants orbiting very close to their suns)—and see if gases like water vapour or methane are present. For the largest planets it will even be able to produce cloud maps and maps of temperature distribution.

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A rendering of the Twinkle mission spacecraft, which will be built by Surrey Satellite Technology Ltd. Image credit: Twinkle/SSTL

Although in the last few years various teams have attempted to discover the composition of exoplanet atmospheres, and molecules such as water have been identified, Twinkle is the first-such dedicated space mission.

Getting above the atmosphere of our own planet is essential to see clearly the atmospheres of others. But it will be no easy task, even though 1888 confirmed exoplanets have been found as of 2 February 2015—many of those found by NASA's Kepler space mission

As lead scientist Professor Giovanna Tinetti of UCL says: “The light filtered through the planet’s atmosphere is only about one ten-thousandth of the overall light from the star. Twinkle is a very ambitious mission and we know very little about these alien worlds.”

Astronomers can measure an exoplanet's mass, density and distance from its star. From that they can deduce its temperature and composition (i.e. small and rocky like Earth, or large and gaseous like Jupiter).

But an atmosphere can make all the difference to the character of a planet and has a large part to play in its temperature. With a surface temperature of 462°C, for example, Venus is hotter than Mercury, whose temperature can fluctuate from -193° to 426°C. This is even though Mercury's a lot closer to the Sun.

The reason is that compared to airless Mercury, Venus has a thick carbon dioxide atmosphere that traps heat. As Tinetti says, “Twinkle will give us a completely new picture of what these worlds are really like.” Sen looks forward to watching Twinkle's progress.

NASA Solar Dynamics Observatory footage of the transit of Venus across the face of the Sun. Twinkle will similarly detect light filtered through the atmosphere of exoplanets as they transit stars. Image credit: NASA/SDO/AIA.