asteroids

Scientists identify water molecules on asteroids for the first time.

Posted by

0


Using data from NASA’s Stratospheric Observatory for Infrared Astronomy (SOFIA), Southwest Research Institute scientists have discovered, for the first time, water molecules on the surface of an asteroid. Scientists looked at four silicate-rich asteroids using the FORCAST instrument to isolate the mid-infrared spectral signatures indicative of molecular water on two of them. Credit: NASA/Carla Thomas/Southwest Research Institute

Using data from the retired Stratospheric Observatory for Infrared Astronomy (SOFIA)—a joint project of NASA and the German Space Agency at DLR—Southwest Research Institute scientists have discovered, for the first time, water molecules on the surface of an asteroid. Scientists looked at four silicate-rich asteroids using the FORCAST instrument to isolate the mid-infrared spectral signatures indicative of molecular water on two of them.

“Asteroids are leftovers from the planetary formation process, so their compositions vary depending on where they formed in the solar nebula,” said SwRI’s Dr. Anicia Arredondo, lead author of a paper in The Planetary Science Journal about the discovery. “Of particular interest is the distribution of water on asteroids, because that can shed light on how water was delivered to Earth.”

Anhydrous, or dry, silicate asteroids form close to the sun while icy materials coalesce farther out. Understanding the location of asteroids and their compositions tells us how materials in the solar nebula were distributed and have evolved since formation. The distribution of water in our solar system will provide insight into the distribution of water in other solar systems and, because water is necessary for all life on Earth, will drive where to look for potential life, both in our solar system and beyond.

“We detected a feature that is unambiguously attributed to molecular water on the asteroids Iris and Massalia,” Arredondo said. “We based our research on the success of the team that found molecular water on the sunlit surface of the moon. We thought we could use SOFIA to find this spectral signature on other bodies.”

SOFIA detected water molecules in one of the largest craters in the moon’s southern hemisphere. Previous observations of both the moon and asteroids had detected some form of hydrogen but could not distinguish between water and its close chemical relative, hydroxyl. Scientists detected roughly equivalent to a 12-ounce bottle of water trapped in a cubic meter of soil spread across the lunar surface, chemically bound in minerals.

“Based on the band strength of the spectral features, the abundance of water on the asteroid is consistent with that of the sunlit moon,” Arredondo said. “Similarly, on asteroids, water can also be bound to minerals as well as adsorbed to silicate and trapped or dissolved in silicate impact glass.”

The data from two fainter asteroids, Parthenope and Melpomene, were too noisy to draw a definitive conclusion. The FORCAST instrument is apparently not sensitive enough to detect the water spectral feature if present. However, with these findings, the team is enlisting NASA’s James Webb Space Telescope, the premier infrared space telescope, to use its precise optics and superior signal-to-noise ratio to investigate more targets.

“We have conducted initial measurements for another two asteroids with Webb during cycle two,” Arredondo said. “We have another proposal in for the next cycle to look at another 30 targets. These studies will increase our understanding of the distribution of water in the solar system.”

A Radio Search for Artificial Emissions from ‘Oumuamua’

Posted by

0


“We were looking for a signal that would prove that this object incorporates some technology …”

 

Oumuamua

An artist’s depiction of interstellar object ‘Oumuamua ESA/Hubble; NASA; ESO; M. Kornmesser

MOUNTAIN VIEW – It’s the first time a visitor from another star system has been seen nearby. But what is it? An asteroid, a comet … or an alien artifact?

Scientists at the SETI Institute have attempted to address this question by using the Allen Telescope Array (ATA) to observe ‘Oumuamua when it was about 170 million miles away, or slightly less than the diameter of Earth’s orbit. The intention was to measure artificial radio transmissions which, if found, would be strong evidence that this object is not simply a rock tossed into space by a random gravitational slingshot interaction that occurred in its home star system.

“We were looking for a signal that would prove that this object incorporates some technology – that it was of artificial origin,” says Gerry Harp, lead author of a paper to be published in the February 2019 issue of Acta Astronautica. “We didn’t find any such emissions, despite a quite sensitive search. While our observations don’t conclusively rule out a non-natural origin for ‘Oumuamua, they constitute important data in assessing its likely makeup.”

Following its discovery in October 2017, ‘Oumuamua was the subject of popular speculation about a possible non-natural origin largely because it brought to mind the interstellar spaceship in Arthur C. Clarke’s novel Rendezvous with Rama. Its highly elongated shape and the fact that no coma was observed strengthened this hypothesis for some, as these are uncharacteristic of asteroids and comets.

A recent paper published in Astrophysical Journal Letters by researchers at Harvard has also suggested the possibility that ‘Oumuamua is a deliberate construction. The Harvard researchers argue that the slight, unexpected acceleration observed for this object could be caused by pressure from sunlight as ‘Oumumua swung around the Sun. Their hypothesis is that the object might be a light sail, either deliberately or accidentally sent our way. A deliberate origin is considered somewhat more likely because our solar system is a very small target for any object that is not being aimed.

Such arguments strengthen the importance of observations such as those conducted on the ATA that can constrain the true nature of ‘Oumuamua.

Observations were made between November 23 and December 5, 2017, using the wide-band correlator of the ATA at frequencies between 1 and 10 GHz and with a frequency resolution of 100 kHz. No signals were found at a level that would be produced by an omnidirectional transmitter on-board the object of a power of about 10 watts or more. In portions of the radio spectrum that are routinely cluttered by artificial satellite telemetry, the threshold for detection was higher. In all cases, these limits to the powers that could be detected are quite modest – comparable to that of a citizen band radio.

While no signals were found coming from ‘Oumuamua, the types of observations reported by SETI Institute scientists may have utility in constraining the nature of any interstellar objects detected in the future, or even the small, well-known objects in our own Solar System. It has been long-hypothesized that some of the latter could be interstellar probes, and radio observations offer a way to address this imaginative, but by no means impossible, idea.

Fresh evidence for how water reached Earth found in asteroid debris

Posted by

0


Water delivery via asteroids or comets is likely taking place in many other planetary systems, just as it happened on Earth, new research strongly suggests.

Published by the Royal Astronomical Society and led by the University of Warwick, the research finds evidence for numerous planetary bodies, including asteroids and comets, containing large amounts of water.

Fresh evidence for how water reached Earth found in asteroid debris

The research findings add further support to the possibility water can be delivered to Earth-like planets via such bodies to create a suitable environment for the formation of life.

Commenting on the findings lead researcher Dr Roberto Raddi, of the University of Warwick’s Astronomy and Astrophysics Group, said:”Our research has found that, rather than being unique, water-rich asteroids similar to those found in our Solar System appear to be frequent. Accordingly, many of planets may have contained a volume of water, comparable to that contained in the Earth.

“It is believed that the Earth was initially dry, but our research strongly supports the view that the oceans we have today were created as a result of impacts by water-rich comets or asteroids”.

In observations obtained at the William Herschel Telescope in the Canary Islands, the University of Warwick astronomers detected a large quantity of hydrogen and oxygen in the atmosphere of a white dwarf (known as SDSS J1242+5226). The quantities found provide the evidence that a water-rich exo- was disrupted and eventually delivered the water it contained onto the star.

The asteroid, the researchers discovered, was comparable in size to Ceres – at 900km across, the largest asteroid in the Solar System. “The amount of water found SDSS J1242+5226 is equivalent to 30-35% of the oceans on Earth”, explained Dr Raddi.

The impact of water-rich asteroids or comets onto a planet or white dwarf results in the mixing of hydrogen and oxygen into the atmosphere. Both elements were detected in large amounts in SDSS J1242+5226.

Research co-author Professor Boris Gänsicke, also of University of Warwick, explained:

“Oxygen, which is a relatively heavy element, will sink deep down over time, and hence a while after the disruption event is over, it will no longer be visible.

“In contrast, hydrogen is the lightest element; it will always remain floating near the surface of the white dwarf where it can easily be detected. There are many that hold large amounts of hydrogen in their atmospheres, and this new study suggests that this is evidence that water-rich asteroids or comets are common around other stars than the Sun”.

Read more at: http://phys.org/news/2015-05-fresh-evidence-earth-asteroid-debris.html#jCp