John McFall, from the United Kingdom, is a member of the ESA Astronaut Class of 2022. John McFall is one of the more than 22 500 candidates who submitted a valid application in 2021 in response to ESA’s call for new astronauts for missions to the International Space Station and beyond. ESA’s new class of astronauts includes career astronauts, members for the astronaut reserve and astronauts with a physical disability for a feasibility project. They will start a 12-month basic training at ESA’s European Astronaut Centre in spring 2023.
Credit: P. Sebirot/ESA

The European Space Agency (ESA), a cooperative space program among the nations of Europe, made history in November 2022, naming the world’s first physically disabled astronaut. Paralympian and orthopedic surgeon John McFall joined 15 others out of 22,500 applicants in the journey to space. McFall had his right leg amputated after a motorcycle accident when he was 19 years old. Before his accident, he was a runner. McFall persevered through recovery and made it to the 2008 Paralympic Games in Beijing, China. He secured the bronze medal in the 100-meter race.

McFall was born on April 25, 1981, in Frimley, England. He was a runner before his accident in 2000. Determined to reach his goals despite his new existence as an amputee, McFall worked through recovery all the way to the Paralympics. He became a professional runner in 2005, only five years after his accident. After his success as a Paralympian, McFall trained as an orthopedic surgeon.

He studied at Swansea University in Wales 2004. He continued his education to earn his master’s degree at the University of Wales Institute in Cardiff in 2005. Not one to shy away from challenges and education, McFall graduated from Cardiff University School of Medicine in 2014. He joined the Royal College of Surgeons in 2016 and works as a trauma and orthopedic specialist in the south of England.

McFall heard that the ESA was looking to hire a Paralympian as an astronaut in February 2021 as he worked in the intensive therapy unit helping patients recover from COVID-19. He started filling out an application and soon was undergoing memory and physical tests and answering difficult questions in interviews.

The ESA named McFall and 15 others as official recruits in November 2022. The group will undergo more testing to ensure their ability to fulfill the role. McFall will take part in the Parastronaut Feasibility Project which will help the ESA understand how space flight works for astronauts with physical disabilities.

January 8, 2020

Late last year, on Dec. 18, 2019, the European Space Agency (ESA) launched the CHEOPS telescope into space, where it will study the composition of exoplanets. Exoplanets, or extrasolar planets, orbit stars other than our sun. The CHEOPS telescope was launched aboard a Russian-made Soyuz rocket from the Guiana Space Center on the northern coast of South America. CHEOPS—pronounced KAY ops—is an acronym for Characterizing Exoplanets Satellite. If the acronym sounds familiar, Cheops was also the Greek name of the ancient Egyptian king Khufu, who constructed the Great Pyramid at Giza.

A Soyuz rocket carrying the ESA’s CHEOPS telescope lifts off from the Guiana Space Center on Dec.18, 2019. Credit: ESA/S. Corvaja

CHEOPS is small for a satellite, measuring just 5 feet (1.5 meters) long. The craft turns within a polar orbit that allows it to fly between night and day. Its back, covered in solar panels, receives continuous sunshine, while the telescope and camera on the other side is always peering into dark, sunless, and limitless space.

This artist’s impression shows CHEOPS with its back to the sun and the telescope pointed into dark space. Credit: ESA/C. Carreau

The CHEOPS mission is not to discover new exoplanets, but rather to learn more about the exoplanets we already know exist. CHEOPS will study exoplanets larger than our own Earth but smaller than the planet Neptune. Scientists want to know if these intermediate sized exoplanets are more like “super-Earths”—large rocky worlds—or “mini-Neptunes”—small gas giants. By studying an exoplanet’s atmosphere, diameter, mass, and other properties, CHEOPS can determine its composition and whether or not it might be able to support life. Astronomers have discovered over 4,000 exoplanets so far, but there are likely hundreds of billions more to be found.

CHEOPS will use the transit method to study exoplanets. It will aim its camera at a star and capture periodic dips in the star’s light output. These dips occur when an exoplanet passes in front of—or transits—a star in relation to CHEOPS’s point of view.

CHEOPS is a stepping stone between the first exoplanet observatories, such as Kepler and COROT, and the powerful observatories of the near future. The United States National Aeronautics and Space Administration (NASA) James Webb Space Telescope (JWST), scheduled for launch in 2021, will be able to determine the gases present in the atmospheres of some exoplanets and even record low detail images of those gases. The European Southern Observatory’s Extremely Large Telescope (ELT) will also be able to image rocky exoplanets and characterize their atmospheres after it is completed in 2025. The ELT is a ground-based observatory being built in the Atacama Desert of northern Chile. Kepler and COROT prepared the way for CHEOPS, and the JWST and ELT will further examine the most promising CHEOPS targets as scientists continue the hunt for extraterrestrial life.

November 9, 2018

On Oct. 20, 2018, an Ariane 5 rocket blasted off from French Guiana, an overseas possession of France on the northern coast of South America. The rocket carried a pair of probes bound for Mercury, the planet in our solar system closest to the sun, as part of a mission called BepiColombo. The mission’s name honors Giuseppe “Bepi” Colombo, an Italian scientist who contributed greatly to the study of Mercury. ESA missions frequently launch from French Guiana at a site called Europe’s Spaceport. The site’s remote geographic location offers advantages in launch trajectory as well as a “slingshot effect” created by the speed of Earth’s rotation near the equator.

The Mercury Planetary Orbiter is one of two probes included in the BepiColombo mission that will study the planet Mercury. Credit: ESA/ATG medialab

The European Space Agency (ESA) developed and organized the BepiColombo mission. ESA led the construction of the Mercury Planetary Orbiter (MPO), the main probe. But two other space agencies contributed to BepiColombo. The United States National Aeronautics and Space Administration (NASA) built an instrument called a mass spectrometer for the MPO. And the Japan Aerospace Exploration Agency (JAXA) built the mission’s second orbiter, the Mercury Magnetospheric Orbiter (MMO). Magnetosphere is the zone of strong magnetic forces that surrounds a heavenly body.

BepiColombo will study Mercury, the innermost planet of the solar system. Credit: NASA Goddard

Mercury, about 48 million miles (77 million kilometers) from Earth, is not a well-studied planet. Only two NASA spacecraft—Mariner 10 and MESSENGER—have reached it so far. In 1974 and 1975, Mariner 10 discovered that Mercury has a strong magnetic field. Scientists had previously thought the planet too small to host a magnetic field. Japan’s MMO is specially designed to study this feature. MESSENGER, which orbited Mercury from 2011 to 2015, learned many things about the scorched planet’s surface and confirmed that water ice existed in permanently shadowed craters at its poles.

Mercury’s magnetic field hints at our solar system’s turbulent early history and unusual composition. Most planetary systems have planets all about the same size and spaced evenly apart. In our solar system, Jupiter, the largest planet, is almost 25,000 times larger than Mercury, the smallest. Mercury might once have been larger, but layers of the planet’s surface could have worn away over billions of years. Alternatively, the planet may simply be the remnant of a collision of earlier inner planets. The BepiColombo mission hopes to learn more about Mercury as well as the formation of our solar system.

BepiColombo is powered by ion propulsion, a method of propelling space vehicles by ejecting charged particles called ions. Ion propulsion increases travel time compared to traditional chemical propulsion, but it costs much less. Ion propulsion also allows a probe to avoid the sun’s powerful gravitational field by taking a long, winding path to Mercury’s orbit. BepiColombo will fly by Earth once, Venus twice, and Mercury six times before it finally enters into orbit around the planet in late 2025.

September 24, 2018

Earlier this year, in April, the European Space Agency (ESA) released the second trove of data gathered by the space probe Gaia (named after the ancient Greek goddess Gaia). Gaia’s precise measurements of the position, brightness, motion, and color of over 1.3 billion stars will transform astronomers’ understanding of our galaxy, the Milky Way.

In this artist’s impression, Gaia maps the stars of the Milky Way. Credit: ESA/ATG medialab/ESO/S. Brunier

The Milky Way contains the sun, Earth, and other objects in our solar system. It also includes hundreds of billions of stars besides the sun. Huge clouds of gas and dust lie throughout the galaxy, and they constantly form new stars. The Milky Way is so massive that about 10 smaller galaxies orbit it like satellites revolving around a planet.

Because our solar system is located within the Milky Way, vast clouds of dust and dense swaths of stars prevent astronomers from determining the galaxy’s exact structure. It is a bit like trying to see the outside of one’s home from the inside. Until now, astronomers had to guess what the Milky Way looks like by observing other galaxies with similar traits—the equivalent of looking at other houses from a window. Astronomers know the Milky Way is a spiral galaxy, with long arms extending out from a central core. But no one knows how many arms it has, what kinds of stars the arms contain, or whether the galaxy is a traditional spiral or a subtype called a barred spiral galaxy where the central core is elongated.

The space probe Gaia will tell us if the Milky Way is a traditional spiral galaxy, as in this illustration, or a barred spiral galaxy with an elongated central core. Credit: Artwork © Jon Lomberg and the National Air and Space Museum

Gaia is like a flying drone taking photos around the neighborhood. Launched in 2013 by the ESA, Gaia traveled to a point behind Earth and began measuring the positions of over a billion stars. Gaia measures stellar distances using a technique called parallax. It first images a star against a background of other stars. Halfway around the sun, it takes another picture of the same star. Because the two pictures are taken from far distant positions, the star moves slightly in relation to its background. This is the same optical effect that makes an object at arm’s length to appear to change positions when viewed from just one eye or the other. Because scientists know how far away the two star pictures were taken, and how much the star appeared to move, they can precisely calculate its distance from Earth.

Gaia’s portrait of the Milky Way also extends into the fourth dimension—time. Over the course of its five-year mission, Gaia will map the sky 29 times. From those time-lapsed maps, astronomers can determine the speed and direction in which the galaxy’s stars and gas clouds are moving through space. This information tells us the origins of Milky Way objects and can even warn of galactic collisions or violent stellar explosions. This time-based study of the galaxy is called galactic archaeology.

Gaia is gathering more than just information about stars. The second data release also had the locations of 14,000 known asteroids within our solar system, allowing astronomers to precisely map their orbits. Future data releases will map even more solar system objects.

ESA released the first Gaia dataset in 2016. For each release, scientists have raced to mine the data for new discoveries. Usually, data from such spacecraft are temporarily reserved for scientists directly associated with the mission. But mission managers have released Gaia’s data to everyone at the same time. This has led to another impressive statistic: over 1,000 peer-reviewed scientific papers that use Gaia’s data have already been written since the first data release. Many thousands more will be written before all Gaia’s insights are revealed.

November 3, 2016

Last month, on October 19, Mars claimed another victim. A landing module named Schiaparelli, designed by the European Space Agency (ESA) and Russia’s space agency, Roscosmos, accidentally smashed into the Martian surface at more than 180 miles (300 kilometers) per hour. Schiaparelli (named for the Italian astronomer Giovanni Schiaparelli, who studied Mars in the late 1800′s) was destroyed, but the mission was not a total failure. The Mars Trace Gas Orbiter (TGO), launched with Schiaparelli, successfully entered into orbit around the Red Planet.

This artist’s impression shows the Trace Gas Orbiter and Schiaparelli (the small circular knob facing toward Mars) during the seven-month ExoMars voyage to the Red Planet. Credit: ESA/David Ducros

Despite is relatively inviting appearance, Mars is extremely difficult to explore. Of all the missions sent there, nearly two-thirds have failed before completing their planned experiments and observations. Landing on Mars is particularly difficult. The planet’s atmosphere is extremely thin, which means that parachutes and similar braking devices don’t work as well as they do in the much denser atmosphere of Earth. Mars is also a relatively large planet, and its significant gravitational pull forces a lander to carry large amounts of fuel for its rockets to slow the descent. On the surface, craggy rocks, enormous sandstorms, and frigid temperatures conspire to damage a lander as it settles into a safe resting place.

The ESA and Roscosmos launched ExoMars 2016, which consisted of Schiaparelli and the TGO, in March of this year. The lander was equipped with a parachute and rockets to slow its entry through the Martian atmosphere. The parachute deployed, but it ejected far too soon. To make matters worse, the rockets, which were supposed to fire for about 30 seconds, fired for only a few seconds before shutting off. Project engineers think these malfunctions stemmed from a software glitch that led the lander to act as though it was already on the Martian surface. Instead, it was actually plummeting through the Martian atmosphere. With nothing to slow it, Schiaparelli crashed into the Red Planet’s surface and exploded.

ExoMars 2016 did not function as the European scientists had hoped, but it could still be a successful mission. Schiaparelli was not intended to add much to the science output of the mission. It had enough power to survive only a few Martian days. Its primary objective was to demonstrate landing technology for the ambitious ExoMars 2020, which will attempt to land a rover on Mars. Mission leaders can take heart in the fact that the lander seems to have been doomed by a software failure, a problem much easier to fix than a hardware failure. But it will be small consolation to an ExoMars program that is already behind schedule and over budget.

The Trace Gas Orbiter, however–a crucial part of the future ExoMars mission–entered into orbit around Mars and appears to be functioning normally. The TGO will examine methane and other gases in the Martian atmosphere. It will help determine if this methane is the result of geological or biological processes. Scientists have not found direct evidence of life on Mars, but some think tiny organisms could exist below its surface. The TGO will also serve as a data relay center for the ExoMars 2020 rover, receiving commands from Earth for the rover and data from the rover to be sent back to Earth. Let’s just hope ESA and Roscosmos can stick the landing on the next try!

October 18, 2016

On September 30, a bright light of science was extinguished in the solar system. That day, the space probe Rosetta crash-landed on the comet it had been orbiting, marking the end of an ambitious mission that paid–and should continue to pay–huge dividends for astronomy.

The European Space Agency (ESA) launched Rosetta on March 2, 2004. Rosetta orbited comet 67P/Churyumov-Gerasimenko from August 2014 to September 2016. Scientists think that comets preserve dust, ice, and rock from the solar system’s formation. By gathering data on a comet, therefore, Rosetta helped scientists to learn more about the solar system’s composition and history. Rosetta was named for the Rosetta stone, an inscribed rock that enabled scholars to interpret ancient Egyptian hieroglyphs. Rosetta also carried a small craft named Philae to land on the surface of the comet’s nucleus (core). Philae was named for the Philae obelisk, which also bore inscriptions that helped decipher ancient Egyptian writing.

This artist’s impression shows the European Space Agency (ESA) lander Philae on the surface of comet 67P/Churyumov-Gerasimenko. Philae was released from the ESA probe Rosetta to gather detailed information about the comet’s structure and makeup. Credit: DLR German Aerospace Center

Rosetta overcame many difficulties to provide key insights into the history of the early universe. It was initially planned as a sample return mission to a different comet in collaboration with the United States National Aeronautics and Space Administration (NASA). But because of the tragic loss of the space shuttle Challenger in 1986, NASA pulled out of the Rosetta mission, and the ESA was forced to scale it back. Many years later, in 2002, an Ariane 5 rocket failed shortly after liftoff. Rosetta was scheduled to be carried into space on the next Ariane 5 later that year. The failure grounded the Ariane 5 for many months, and mission scientists changed their target comet to 67P/Churyumov-Gerasimenko.

In 2014, when the lander Philae touched down on 67P, its landing harpoons failed to trigger. The craft bounced high into space and came down on its side in a sunless area of the comet’s nucleus. Scientists worked feverishly to conduct experiments and gather data for 57 hours before the lander’s solar-powered batteries died. Despite Philae’s loss, Rosetta continued orbiting the comet, taking photographs and collecting data. On Sept. 2, 2016, with just weeks left in the mission, Rosetta discovered the wayward Philae in the shade of a small cliff on the comet’s surface.

In spite of all the bumps along the way, Rosetta was a fabulously successful mission. It became the first spacecraft to orbit a comet, and it released the first probe to land on (rather than crash into) a comet. It returned invaluable data about the evolution of comets as they approach the sun and the history of the early solar system. Scientists are only just beginning to draw conclusions from Rosetta’s data.

Rosetta’s collision with the comet was not accidental, but had been planned by mission scientists. The highly elliptical (elongated) orbit of 67P takes it as close as 115 million miles (185 million kilometers) and as far as 530 million miles (850 million kilometers) from the sun. This creates vast and lengthy temperature changes over the course of its six-and-a-half-year orbit. These temperature extremes ravage a spacecraft’s sensors and electronic equipment. As the comet tracked back away from the sun, scientists feared that Rosetta could not survive another hibernation in the icy depths of the outer solar system. Rather than risk it, they decided to send Rosetta out in style, crashing into the comet while collecting as much data as possible. On its final descent, Rosetta studied the comet’s gas, dust, and plasma environment very close to the surface. The probe also took some harrowing high-resolution images as it plunged toward the comet.

Despite the end of Rosetta, ESA has several other important missions in progress. LISA Pathfinder plans to study gravitational waves from space. The Gaia probe is in the process of creating the most detailed map of the galaxy ever. The ExoMars Trace Gas Orbiter is en route to Mars to study the planet’s atmosphere and release a lander in preparation for a future wheeled rover.

September 23, 2016

The Milky Way Galaxy is our home, but we know surprisingly little about it. Last week, on September 14, the European Space Agency (ESA) released a wealth of data gathered by the space probe Gaia (named after the ancient Greek goddess Gaia). The probe pinned down the precise position and brightness of over a billion stars. As massive as this dataset seems, it represents just a taste of what is to come from Gaia, which promises to revolutionize the study of our galaxy in the next several years.

This artist’s impression shows Gaia mapping the stars of the Milky Way. Credit: ESA/ATG medialab/ESO/S. Brunier

The Milky Way contains the sun, Earth, and other objects in our solar system. It also includes hundreds of billions of stars besides the sun. Huge clouds of gas and dust lie throughout the galaxy, and they constantly form new stars. The Milky Way is so massive that about 10 smaller galaxies orbit it like satellites revolving around a planet.

Because our solar system is located within the Milky Way, vast clouds of dust and dense swaths of stars prevent astronomers from determining the galaxy’s exact structure. It’s a bit like trying to figure out what the outside of one’s home looks like while being trapped inside. Until now, astronomers had to guess what the Milky Way looks like by observing other galaxies with similar traits—the equivalent of looking at other houses from a window. Gaia, however, is like a drone taking photos around the neighborhood. Launched in 2013 by the ESA, Gaia traveled to a point behind Earth and began measuring the positions of over a billion stars as it orbited the sun.

Gaia measures stellar distances using a technique called parallax. It first images a star against a background of other stars. Halfway around the sun, it takes another picture of the same star. Because the two pictures are taken many millions of miles apart, the star’s position changes slightly in relation to its background. This is the same effect that causes an object at arm’s length to appear to change positions when viewed from one eye or the other at a time. Because scientists know how far away the two star pictures were taken, and how much the star appeared to move, they can calculate its distance from Earth.

Gaia’s first map shows a two-dimensional plot of star density in the Milky Way. As Gaia orbits the sun, it will gather information on more and more points of light. It will then be able to refine its data to better define star positions. Astronomers are confident that future data from Gaia will allow them to create extremely accurate, three-dimensional maps of the galaxy.

Furthermore, as Gaia’s mission continues, its portrait of the Milky Way will extend into four dimensions (including time). As it observes over the years, Gaia will be able to detect the speed and direction in which stars are moving through space. This information will allow astrophysicists to see what the galaxy looked like in the recent past and to predict what it will look like in the near future.

December 18, 2015

On Tuesday, the United Kingdom sent its first publicly funded astronaut to the International Space Station (ISS). Tim Peake, an astronaut of the European Space Agency (ESA), arrived at the station six hours after launch aboard a Russian Soyuz spacecraft. During his six-month stay at the ISS, he will help conduct scientific experiments and perform public outreach. Peake joins American astronaut Scott Kelly and Russian cosmonauts Sergey Volkov and Mikhail Korniyenko aboard the station. He flew up together with Russian cosmonaut Yuri Malenchenko and American astronaut Timothy Kopra. Together, the six men make up the 46^th expedition to the ISS.

Tim Peake became the first publicly funded British astronaut aboard the International Space Station on Dec. 15, 2015. Credit: Victor Zelentsov, NASA/ESA Credit: Victor Zelentsov, NASA/ESA

An astronaut is a person who pilots a spacecraft or works in space. Astronauts operate spacecraft and space stations, launch and recapture satellites, and conduct scientific experiments. The word astronaut comes from Greek words meaning sailor among the stars. Cosmonaut is a Russian word that means sailor of the universe.

Peake is not the first British citizen to be launched into space. In 1991, chemist Helen Sharman visited the Russian space station Mir as part of a project funded partly by British companies. Several other astronauts with dual British and United States citizenship have worked in space as members of the United States’ National Aeronautics and Space Administration (NASA).

In the past, the British government was reluctant to participate in manned spaceflight. It formally rejected training astronauts in 1986. But over time, decreasing costs and safety concerns, combined with the chance to bolster national pride and public interest in the sciences, caused the government to change course. In 2008, the British National Space Centre released a new space strategy document in which it expressed an openness to manned missions. After many years of difficult training, Tim Peake blasted off wearing the Union Jack flag patch on his spacesuit. The United Kingdom, known for its daring exploration of remote parts of the world in centuries past, has now begun manned exploration of space.

Additional World Book articles:

• Space exploration (1994) – A Back in Time article
  
• Space exploration (2000) – A Back in Time article
• Space exploration (2003) – A Back in Time article
• Space exploration (2008) – A Back in Time article

January 7, 2015

New images from the Hubble Space Telescope show the Pillars of Creation in the turbulent Eagle Nebula in even sharper detail. The original image of the Pillars, taken in 1995, may be the most famous of all the astonishing images of space objects captured by the orbiting telescope. The new image was made using a wide-field camera that was installed on Hubble on 2009. The camera produces images with twice the resolution of the camera that made the original image.

The Eagle Nebula, which is some 7,000 light-years away, is an open cluster of stars with several areas of active star formation, including the Pillars of Creation. The Pillars are actually columns of cool interstellar hydrogen gas and dust. In the new false-color image (above, right), areas giving off oxygen are blue; areas giving off sulfur are orange; and areas giving off hydrogen and nitrogen are green. (NASA, ESA, STScI, and J. Hester and P. Scowen (Arizona State University); NASA, ESA, and the Hubble Heritage Team (STScI/AURA)

The nebula got its nickname because of the high rate at which stars are being born there. “These pillars represent a very dynamic, active process,” said Paul Scowen of Arizona State University in Tempe, who, with astronomer Jeff Hester, formerly of Arizona State University, led the original Hubble observations of the Eagle Nebula. “The gas is not being passively heated up and gently wafting away into space. The gaseous pillars are actually getting ionized (a process by which electrons are stripped off of atoms) and heated up by radiation from the massive stars. And then they are being eroded by the stars’ strong winds (barrage of charged particles), which are sandblasting away the tops of these pillars.”

In another new Hubble image of the Pillars, taken in near-infrared light, the objects appear in silhouette. The bluish haze around the dense edges of the Pillars is material getting heated up by the intense ultraviolet radiation from a cluster of young, massive stars and evaporating away into space. (NASA, ESA, and the Hubble Heritage Team (STScI/AURA)

Scowen noted that the sun formed as part of a cluster that included stars massive enough to produce powerful ionizing radiation, like those in the Eagle Nebula. “What that means is when you look at the environment of the Eagle Nebula or other star-forming regions, you’re looking at exactly the kind of nascent environment that our Sun formed in,” he said.

Additional World Book articles:

• Astronomy
• Astronomy Through a Millennium (a special report)
• Seeing the Universe in a Different Light (a special report)
• The Universe on the Grand Scale (a special report)
• Telescopes: 400 Years of Stargazing (a special report)

November 14, 2014

Yesterday, the robot probe Philae began sending back the first images ever taken from the fractured terrain of a comet. After an awkward landing in which the probe bounced twice, initially back out into space, it stabilized on Comet 67P. It is currently attempting to drill into the surface of the comet. European Space Agency (ESA) scientists hope the tool will be able to capture some samples for analysis in Philae’s on-board laboratories.

An artist’s impression of the probe Philae (front view) on the surface of Comet 67P. (ESA/ATG medialab)

The objective of this ESA mission is to explore the origins of our solar system. Comets are believed to hold materials that are largely unchanged since the formation of the planets 4.6 billion years ago. Scientists speculate that comets delivered water to the early Earth. Others theorize that comets could even have “seeded” Earth with the chemicals needed to start life on the planet.

From the pictures Philae has returned to Earth, the ESA scientists believe it landed in the shadow of a cliff, meaning that the sunlight the probe receives is limited. As a result, its solar panels probably will not keep the battery systems properly charged, cutting short the run of the mission.

ESA’s Rosetta satellite, with its piggybacked Philae lander, was launched in 2004. The pair traveled 4 billion miles (6.4 billion kilometers) to reach Comet 67P, out near the orbit of Jupiter. After a long period of maneuvering into the correct position, Rosetta dropped Philae onto to Comet 67P on November 12.

Additional World Book articles:

• Comet (a Research Guide)
• Space exploration

For additional information about the Rosetta missions, see: http://rosetta.esa.int/