Shannon Stirone, Author at ��è��Ƶ

We now know more on the origins of weird duck-shaped comet 67P

Shannon Stirone — Fri, 27 Oct 2017 15:13:09 +0000

Window on the past

ESA/Rosetta/NavCam

The famed “rubber duck” comet is revealing more about its past. It turns out that 67P/Churyumov-Gerasimenko probably did grow out of tiny pebbles, as many suspected – and this may help us learn more on how planets are built too.

When the Rosetta spacecraft launched towards 67P in 2004, part of its mission was to figure out how the weird, double-lobed comet formed. Using data from Rosetta and its accompanying lander, Philae, at Braunschweig University of Technology in Germany and his colleagues have traced the comet’s building blocks to tiny pebbles of dust and ice.

To help uncover 67P’s origin story, Blum and his team studied the data compiled after the end of the Rosetta mission and compared the observations with models of how planets and other, smaller space rocks form.

As the solar system formed, these microscopic dust and ice pebbles made up a disc around the sun. The same disc that probably formed comet 67P also built all the planets in our solar system, including Earth.

��è��Ƶs have long suspected that these clumps of microscopic dust are gradually attracted to one another over time, and gravity slowly builds a bigger and bigger pile of pebbles. This process, called gentle gravitational collapse, can eventually form a dusty comet such as 67P, which is about 4.3 kilometres long – or even an entire planet.

Blum and his colleagues confirmed that 67P was almost certainly formed through gentle gravitational collapse.

Duck mystery

However, this analysis does not solve the mystery of how 67P got its rubber-duck-like shape. “Whether the two lobes were once one body and then carved out to its current shape, or came together in a gentle collision by two individual bodies, we have no information about in our paper,” says Blum.

Comets such as 67P are relics of the beginning of the solar system. Because comets spend most of their time on the outskirts of our solar system, they don’t melt or get bombarded with particles from the sun – thus serving as valuable time capsules to billions of years ago.

“This is really fundamental work because the greatest question we have is how comets form,” says , a project scientist for the Rosetta mission. “They are the primitive building blocks and tell us how planetesimals form.”

Given that planetesimals can later grow into full-sized planets, understanding comets such as 67P could help us gain more insight into how planets form in general. By tracing these comets back to the pebbles that made them, we can find out more about what kinds of material made Earth.

Journal reference: Monthly Notices of the Royal Astronomical Society, DOI:

One of Europa’s plumes may not exist, making hunt for life hard

Shannon Stirone — Tue, 29 Aug 2017 16:45:55 +0000

Are they there?

NASA

Jupiter’s icy moon Europa is believed to be one of the most promising places to search for alien microbes, thanks to the presence of a subsurface ocean. Plumes of water thought to emerge from the surface would make it even easier to hunt for life – but it now seems these plumes could just be warm rocks. Key to the mystery is a property called thermal inertia, a measure of how quickly a material absorbs and releases heat, which is different for all rocky material. For example, sand has a low thermal inertia, heating up quickly during the day and cooling fast at night. Larger pebbles or boulders take a while to heat up, but retain that warmth well into the night. This slower kind of retention could be taking place at the Pwyll crater on Europa. NASA’s Galileo probe, which orbited Jupiter between 1995 and 2003, observed a “hotspot” in this crater – normally indicative of an underground heat source that could fuel a spout of water. But although researchers suspected the heat source may be a plume, the results were never confirmed. Now Samantha Trumbo and Mike Brown at the California Institute of Technology have used the ALMA telescope array in Chile to watch the anomalous spot during Europa’s daytime and compared it to the night-time observations previously made by Galileo. “All we can say is that our data are not consistent with a current subsurface heat source,” says Trumbo. “That doesn’t necessarily mean there’s no plume there.” It just means that they’re not seeing a heat signature with that plume like they have on Enceladus, Saturn’s icy moon.

Sampling from space

Testing the liquid that researchers strongly suspect lies beneath Europa’s icy crust would be easier if material was being shot out into space, where a spacecraft could collect samples. The alternative would involve the tricky feat of finding a way to drill through the thick ice. There is still hope, even if there are no plumes in that spot: previous observations with the Hubble Space Telescope hint at possible plumes elsewhere on Europa, but the ALMA results may have crossed the Pwyll crater off the list. Two spacecraft missions are planned to visit Europa in the 2020s, so finding out whether the plumes exist in advance is a top priority. Trumbo and Brown have been approved for more telescope time on ALMA, where they will dig deeper into the mysteries of the Pwyll hotspot in the hope of finding an answer. “It’s really interesting, because one of the big problems we have with Europa is the lack of data,” says Cynthia Phillips at NASA’s Jet Propulsion Laboratory. “If there was a confirmed plume, that would be really exciting, but if there’s no plume, it doesn’t mean the ocean is less habitable.” Journal reference:

Shannon Stirone, Author at ��è����Ƶ

We now know more on the origins of weird duck-shaped comet 67P

Duck mystery

One of Europa’s plumes may not exist, making hunt for life hard

Sampling from space

Shannon Stirone, Author at ��è��Ƶ