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Joint missions to Mars

NASA and the European Space Agency (ESA) have embarked on a joint program to explore Mars in the coming decades and selected the five science instruments for the first mission.

The ExoMars Trace Gas Orbiter, scheduled to launch in 2016, is the first of three joint robotic missions to the Red Planet. It will study the chemical makeup of the Martian atmosphere with a 1,000-fold increase in sensitivity over previous Mars orbiters.

The mission will focus on trace gases, including methane, which could be potentially geochemical or biological in origin and be indicators for the existence of life on Mars.

The mission also will serve as an additional communications relay for Mars surface missions beginning in 2018.

“Independently, NASA and ESA have made amazing discoveries up to this point,” said Ed Weiler, associate administrator of NASA’s Science Mission Directorate in Washington.

“Working together, we’ll reduce duplication of effort, expand our capabilities and see results neither ever could have achieved alone.”

First five scientific instruments selected

NASA and ESA invited scientists worldwide to propose the spacecraft’s instruments. The five selected were from 19 proposals submitted in January. Both agencies evaluated the submissions and chose those with the best science value and lowest risk.

Map of methane in Mars' atmosphere

The ExoMars Trace Gas Orbiter will map the variation of Martian methane with unprecedented accuracy, helping to determine whether it is biologically or volcanically produced.

The selection of the instruments begins the first phase of the new NASA-ESA alliance for future ventures to Mars. The instruments and the principal investigators are:

  • Mars Atmosphere Trace Molecule Occultation Spectrometer — A spectrometer designed to detect very low concentrations of the molecular components of the Martian atmosphere.
  • High Resolution Solar Occultation and Nadir Spectrometer — A spectrometer designed to detect traces of the components of the Martian atmosphere and to map where they are on the surface.
  • ExoMars Climate Sounder — An infrared radiometer that provides daily global data on dust, water vapour and other materials to provide the context for data analysis from the spectrometers.
  • High Resolution Colour Stereo Imager — A camera that provides four-colour stereo imaging at a resolution of two million pixels over an 8.5 kilometre (5.3 mile) swath.
  • Mars Atmospheric Global Imaging Experiment — A wide-angle, multi-spectral camera to provide global images of Mars in support of the other instruments.

The science teams on all the instruments have broad international participation from Europe and the United States, with important hardware contributions from Canada and Switzerland.

“To fully explore Mars, we want to marshal all the talents we can on Earth,” said David Southwood, ESA director for Science and Robotic Exploration.

Artist's impression of the ExoMars Trace Gas Orbiter spacecraft

Artist's impression of the ExoMars Trace Gas Orbiter spacecraft, scheduled for launch in 2016. It will carry five science instruments plus an entry, descent and landing test vehicle.

“Now NASA and ESA are combining forces for the joint ExoMars Trace Gas Orbiter mission. Mapping methane allows us to investigate further that most important of questions: Is Mars a living planet, and if not, can or will it become so in the future?”

Common purpose in Mars exploration

NASA and ESA share a common interest in conducting robotic missions to the Red Planet for scientific purposes and to prepare for possible human visits.

After a series of extensive discussions, the science heads of both agencies agreed on a plan of cooperation during a July 2009 meeting in Plymouth, England, later confirmed by ESA Director General Jean-Jacques Dordain and NASA Administrator Charles Bolden in a statement of intent that was signed in November 2009.

The plan consists of two Mars cooperative missions in 2016 and 2018, and a later joint sample return mission.

The 2016 mission features the European-built ExoMars Trace Gas Orbiter, a European-built small lander demonstrator, a primarily-US international science payload, and NASA-provided launch vehicle and communications components. ESA member states will provide additional instrument support.

The 2018 mission consists of a European rover with a drilling capability, a NASA rover capable of caching selected samples for potential future return to Earth, a NASA landing system, and a NASA launch vehicle.

These activities are designed to serve as the foundation of a cooperative program to increase science returns and move the agencies toward a joint Mars sample return mission in the 2020s.

Adapted from information issued by JPL / ESA / NASA.

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A planet that “tastes” funny

Artist's concept of an unusual, methane-free planet

A distant planet is partially eclipsed by its star in this artist's concept. NASA's Spitzer Space Telescope has found evidence that the hot, Neptune-sized planet lacks methane — an ingredient common to many planets in our own Solar System.

NASA’s Spitzer Space Telescope has discovered something odd about a distant planet — it lacks methane, an ingredient common to many of the planets in our Solar System.

“It’s a big puzzle,” said Kevin Stevenson, a planetary sciences graduate student at the University of Central Florida in Orlando, lead author of a study appearing in the journal Nature.

“Models tell us that the carbon in this planet should be in the form of methane. Theorists are going to be quite busy trying to figure this one out.”

The discovery brings astronomers one step closer to probing the atmospheres of distant planets the size of Earth.

The methane-free planet, called GJ 436b, is about the size of Neptune, making it the smallest distant planet that any telescope has successfully “tasted,” or analysed.

Eventually, a larger space telescope could use the same kind of technique to search smaller, Earth-like worlds for methane and other chemical signs of life, such as water, oxygen and carbon dioxide.

“Ultimately, we want to find bio-signatures on a small, rocky world. Oxygen, especially with even a little methane, would tell us that we humans might not be alone,” said Stevenson.

Plots from NASA's Spitzer Space Telescope showing light from GJ 436b, and its star, measured at six different wavelengths.

The Spitzer Space Telescope measured the light from a distant planet, GJ 436b, and its star, at six different wavelengths, before, during and after the planet circled behind the star. The dips tell astronomers how much light is coming from the planet itself. The differences at different wavelengths give clues as to what gases are in the planet's atmosphere.

“In this case, we expected to find methane not because of the presence of life, but because of the planet’s chemistry. This type of planet should have cooked up methane. It’s like dipping bread into beaten eggs, frying it, and getting oatmeal in the end,” said Joseph Harrington of the University of Central Florida, the principal investigator of the research.

Does methane indicate the presence of life?

Methane is present on our life-bearing planet, manufactured primarily by microbes living in cows and soaking in waterlogged rice fields.

All of the giant planets in our Solar System have methane too, despite their lack of cows. Neptune is blue because of this chemical, which absorbs red light.

Methane is a common ingredient of relatively cool bodies, including “failed” stars, which are called brown dwarfs.

In fact, any world with the common atmospheric mix of hydrogen, carbon and oxygen, and a temperature up to 730 degrees Celsius is expected to have a large amount of methane and a small amount of carbon monoxide. The carbon should “prefer” to be in the form of methane at these temperatures.

At 530 degrees Celsius, GJ 436b is supposed to have abundant methane and little carbon monoxide. Spitzer observations have shown the opposite. The space telescope has captured the planet’s light in six infrared wavelengths, showing evidence for carbon monoxide but not methane.

“We’re scratching our heads,” said Harrington. “But what this does tell us is that there is room for improvement in our models. Now we have actual data on faraway planets that will teach us what’s really going on in their atmospheres.”

Aiming to find Earth-like planets

GJ 436b is located 33 light-years away. It rides in a tight, 2.64-day orbit around its small star, an “M-dwarf” much cooler than our sun. The planet transits, or crosses in front of, its star as viewed from Earth.

Artist's impression of the Spitzer Space Telescope

Artist's impression of the Spitzer Space Telescope, which made the observations.

Spitzer was able to detect the faint glow of GJ 436b by watching it slip behind its star, an event called a secondary eclipse. As the planet disappears, the total light observed from the star system drops — this drop is then measured to find the brightness of the planet at various wavelengths.

The technique, first pioneered by Spitzer in 2005, has since been used to measure atmospheric components of several Jupiter-sized exoplanets, the so-called “hot Jupiters“, and now the Neptune-sized GJ 436b.

“The Spitzer technique is being pushed to smaller, cooler planets more like our Earth than the previously studied hot Jupiters,” said Charles Beichman, director of NASA’s Exoplanet Science Institute at NASA’s Jet Propulsion Laboratory and the California Institute of Technology.

“In coming years, we can expect that a space telescope could characterise the atmosphere of a rocky planet a few times the size of the Earth. Such a planet might show signposts of life.”

Adapted from information issued by NASA / JPL-Caltech / K. Stevenson (U. of Central Florida).