ESA Rosetta Mission: ROSINA water vapour discovery

ESA announced the latest important discovery regarding comet 67P/Churyumov–Gerasimenko.

Rosetta spacecraft orbiting the comet has found the water vapour from its target to be significantly different to that found on Earth.

The discovery made by Rosetta Orbiter Spectrometer for Ion and Neutral Analysis (ROSINA) fuels the debate on the origin of our planet's oceans.

That's not all, ESA's Rosetta project scientist, Matt Taylor, believes that ROSINA will make more key findings for our understanding of the origin of life. "ROSINA is continuing to take measurements and will for the rest of the mission," Taylor told reporters.

"It is making and will make invaluable detections of the composition of the comets atmosphere, as well as monitoring its density."

ROSINA is a combination of two mass spectrometers and a pressure sensor. The mass spectrometers determine the composition of the comet's atmosphere and ionosphere, measure the temperature and bulk velocity of the gas and ions, and investigate reactions in which they take part.

The ROSINA pressure sensor is capable of measuring both total and ram pressure, and will be used to determine the gas density and rate of radial gas flow.

"It can detect many different kinds of molecules and get to the heart of the constituents of the ancient comet, giving us unprecedented insight into what the conditions were at the beginning of the solar system," Taylor revealed.

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No single instrument could have the capabilities required to accomplish the ROSINA science objectives, so a three-sensor approach has been adopted.

Each sensor is optimized for a part of the scientific objectives, while at the same time complementing the other sensors.

The latest results were the most anticipated, because the origin of Earth's water is still an open question.

Taylor noticed that those findings have put recent Herschel results into context and agree with results from the Giotto mission.

"It is a very important result and was of the most anticipated, if only that it was one of the first we would be able to make," he said.

In January 2014, ESA's Herschel mission discovered water vapor around dwarf planet Ceres, and in 1986, ESA's Giotto was the first spacecraft to make close up observations of a comet.

Comets in particular are unique tools for probing the early Solar System. They harbor material left over from the protoplanetary disc out of which the planets formed, and therefore should reflect the primordial composition of their places of origin.

ESA Rosetta: First measurements of Comet 67/P’s water ratio

ESA Rosetta’s measurement of the deuterium-to-hydrogen ratio (D/H) measured in the water vapour around Comet 67P/Churyumov–Gerasimenko. 

The measurements were made using ROSINA’s DFMS double focusing mass spectrometer between 8 August and 5 September 2014.

Credit: ESA, DLR.

Deuterium is an isotope of hydrogen with an added neutron.

The ratio of deuterium to hydrogen in water is a key diagnostic to determining where in the Solar System an object originated and in what proportion asteroids and/or comets contributed to Earth’s oceans.

The graph displays the different values of D/H in water observed in various bodies in the Solar System.

The data points are grouped by colour as planets and moons (blue), chondritic meteorites from the Asteroid Belt (grey), comets originating from the Oort cloud (purple) and Jupiter family comets (pink). Rosetta’s Jupiter-family comet is highlighted in yellow.

Diamonds represent data obtained in situ; circles represent data obtained by astronomical methods.

The lower part of the graph shows the value of D/H measured in molecular hydrogen in the atmosphere of the giant planets of the Solar System (Jupiter, Saturn, Uranus, Neptune) and an estimate of the typical value in molecular hydrogen for the protosolar nebula, from which all objects in our Solar System formed.

The ratio for Earth’s oceans is 1.56 ×10–4 (shown as the blue horizontal line in the upper part of the graph).

The value for Comet 67P/Churyumov–Gerasimenko is found to be 5.3 x 10–4, more than three times greater than for Earth’s oceans.

The discovery fuels the debate on the origin of Earth’s oceans and whether asteroids or comets played the bigger role in delivering water.

ESA Rosetta: Earth's Water Came from Asteroids, Not Comets

ESA Rosetta’s navigation camera obtained the four images in this mosaic on Dec. 7, 2014, from a distance of 12.2 miles (19.7 km) from the center of Comet 67P/Churyumov-Gerasimenko.

Credit: ESA/Rosetta/NAVCAM – CC BY-SA IGO 3.0

Asteroids, not comets, may have delivered most of Earth's water to the planet when the solar system was young, new data from the ESA Rosetta probe orbiting comet 67/P suggests.

Comets are some of the solar system's most primitive building blocks, with many dating to soon after its formation.

Scientists think that these dirty snowballs probably helped seed Earth with key ingredients for life, such as organic compounds.

The European Space Agency's (ESA) Rosetta spacecraft is helping scientists learn more about the role these icy nomads have played in the evolution of the solar system and life on Earth by analyzing the composition of Comet 67P/Churyumov–Gerasimenko.

In August, Rosetta became the first spacecraft to orbit a comet, and in November, its Philae lander became the first probe to make a soft touchdown on a comet's surface.

Rosetta is also the first mission to escort a comet as it travels around the sun.

Now, Rosetta has helped solve a mystery about how Earth became the watery world it is today.

Before Rosetta began orbiting Comet 67P/C-G in August, it was using an instrument known as ROSINA (short for Rosetta Orbiter Spectrometer for Ion and Neutral Analysis) to analyze the chemical fingerprint of gases in the comet's fuzzy envelope.

Scientists focused on data from the instrument regarding water to help uncover whether asteroids or comets delivered the water in Earth's oceans.

Rosetta has provided data from Comet 67P/C-G, another Kuiper Belt comet.

However, Rosetta has discovered that this comet possesses an even higher deuterium-to-hydrogen ratio than seen in Oort Cloud comets, three times the amount of heavy water compared to normal water as Earth has.

If Earth's water had come from Kuiper Belt objects, even if most of them were like comet 103P/Hartley 2, and if only a small fraction were like Comet 67P/C-G, Earth's deuterium-to-hydrogen ratio would be significantly higher than it is today.

"This probably rules out Kuiper Belt comets from bringing water to Earth," Altwegg said. Instead, most of Earth's water was probably delivered by asteroids, Altwegg said.

"Today's asteroids have very little water, that's clear," Altwegg added. "But that was probably not always the case. During the Late Heavy Bombardment 3.8 billion years ago, at that time, asteroids could have had much more water than they could now."

The asteroids seen now "have stayed in the vicinity of the sun for 4.6 billion years," Altwegg said.

"They've lost water due to the sun, due to heat. But to start with, they might have had much more water than they have now."

Future analysis of ice-rich bodies in the asteroid belt could shed light on whether Earth's water really did come from there, Altwegg said.