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Black hole candidate and host galaxy

BARCELONA, (ESA).- ESA’s XMM-Newton observatory has discovered the best-ever candidate for a very rare and elusive type of cosmic phenomenon: a medium-weight black hole in the process of tearing apart and feasting on a nearby star.

There are various types of black hole lurking throughout the Universe: massive stars create stellar-mass black holes when they die, while galaxies host supermassive black holes at their centres, with masses equivalent to millions or billions of Suns.

Lying between these extremes is a more retiring member of the black hole family: intermediate-mass black holes. Thought to be seeds that will eventually grow to become supermassive, these black holes are especially elusive, and thus very few robust candidates have ever been found.

Now, a team of researchers using data from ESA’s XMM-Newton X-ray space observatory, as well as NASA’s Chandra X-Ray Observatory and Swift X-Ray Telescope, has found a rare telltale sign of activity. They detected an enormous flare of radiation in the outskirts of a distant galaxy, thrown off as a star passed too close to a black hole and was subsequently devoured.

“This is incredibly exciting: this type of black hole hasn’t been spotted so clearly before,” says lead scientist Dacheng Lin of the University of New Hampshire, USA.

“A few candidates have been found, but on the whole they’re extremely rare and very sought after. This is the best intermediate-mass black hole candidate observed so far.”

This breed of black hole is thought to form in various ways. One formation scenario is the runaway merger of massive stars lying within dense star clusters, making the centres of these clusters one of the best places to hunt for them. However, by the time such black holes have formed, these sites tend to be devoid of gas, leaving the black holes with no material to consume and thus little radiation to emit – which in turn makes them extremely difficult to spot.

“One of the few methods we can use to try to find an intermediate-mass black hole is to wait for a star to pass close to it and become disrupted — this essentially ‘activates’ the black hole’s appetite again and prompts it to emit a flare that we can observe,” adds Lin.

“This kind of event has only been clearly seen at the centre of a galaxy before, not at the outer edges.”

Lin and colleagues sifted through data from XMM-Newton to find the candidate. They identified it in observations of a large galaxy some 740 million light-years away, taken in 2006 and 2009 as part of a galaxy survey, and in additional data from Chandra (2006 and 2016) and Swift (2014).

“We also looked at images of the galaxy taken by a whole host of other telescopes, to see what the emission looked like optically,” says co-author Jay Strader of Michigan State University, USA.

“We spotted the source flaring in brightness in two images from 2005 — it appeared far bluer and brighter than it had just a few years previously. By comparing all the data we determined that the unfortunate star was likely disrupted in October 2003 in our time, and produced a burst of energy that decayed over the following 10 years or so.”

The scientists believe that the star was disrupted and torn apart by a black hole with a mass of around fifty thousand times that of the Sun.

Dust stoms on Titan spotted by Cassini for the first time

BARCELONA, (ESA).-Data from the international Cassini spacecraft that explored Saturn and its moons between 2004 and 2017 has revealed what appear to be giant dust storms in equatorial regions of Titan. 

The discovery, described in a paper published in Nature Geoscience today, makes Titan the third body in the Solar System where dust storms have been observed – the other two are Earth and Mars.   

The observation is helping scientists to better understand the fascinating and dynamic environment of Saturn’s largest moon. 

“Titan is a very active moon,” says Sebastien Rodriguez, an astronomer at the University Paris Diderot, France, and the lead author of the paper.  

“We already know that about its geology and exotic hydrocarbon cycle. Now we can add another analogy with Earth and Mars: the active dust cycle.” 

Complex organic molecules, which result from the atmospheric chemistry and, once large enough, eventually fall to the surface, can be raised from large dune fields around Titan’s equator. 

Titan is an intriguing world – in a way quite similar to Earth. In fact, it is the only moon of the Solar System with a substantial atmosphere and the only celestial body other than our planet where stable bodies of surface liquid are known to still exist.  

There is one big difference though: while on Earth such rivers, lakes and seas are filled with water, on Titan it is primarily methane and ethane that flows through these liquid reservoirs. In this unique methane cycle, the hydrocarbon molecules evaporate, condense into clouds and rain back onto the ground.  

The weather on Titan varies from season to season, just as it does on Earth. In particular around the equinox, the time when the Sun crosses Titan’s equator, massive clouds can form in tropical regions and cause powerful methane storms. Cassini observed such storms during several of its Titan flybys.  

When Sébastien and his team first spotted three unusual equatorial brightenings in infrared images taken by Cassini around the moon’s 2009 northern equinox, they thought these might be exactly such methane clouds. A thorough investigation revealed they were something completely different, however. 

“From what we know about cloud formation on Titan, we can say that such methane clouds in this area and in this time of the year are not physically possible,” says Sébastien. 

“The convective methane clouds that can develop in this area and during this period of time would contain huge droplets and must be at a very high altitude, much higher than the 10 km that modelling tells us the new features are located.”
The researchers were also able to rule out that the features were actually on the surface in the form of frozen methane rain or icy lavas. Such surface spots would have a different chemical signature and remain visible for much longer, while the bright features in this study were only visible for 11 hours to five weeks. 

Modelling also showed that the features must be atmospheric, but still close to the surface – most likely forming a very thin layer of tiny solid organic particles. Since they were located right over the dune fields around Titan’s equator, the only remaining explanation was that the spots were actually clouds of dust raised from the dunes.
Sébastien says that while this is the first ever observation of a dust storm on Titan, the finding is not surprising. 

“We believe that the Huygens probe, which landed on the surface of Titan in January 2005, raised a small amount of organic dust upon arrival due to its powerful aerodynamic wake,” says Sébastien. 

“But what we spotted here with Cassini is at a much larger scale. The near-surface wind speeds required to raise such an amount of dust as we see in these dust storms would have to be very strong – about five times as strong as the average wind speeds estimated by the Huygens measurements near the surface and with climate models.”

Huygens made only one direct measurement of the speed of the surface wind just before its landing on Titan, and at that time it was very low, less than 1 metre per second.  

“For the moment, the only satisfactory explanation for these strong surface winds is that they might be related to the powerful gusts that may arise in front of the huge methane storms we observe in that area and season,” concludes Sébastien.  

This phenomenon, called ‘haboob’, can also be observed on Earth with giant dust clouds preceding storms in arid areas. 

The existence of such strong winds generating massive dust storms also implies that the underlying sand can be set in motion, too, and that the giant dunes covering Titan’s equatorial regions are still active and continually changing.   

The winds could be transporting the dust raised from the dunes across large distances, contributing to the global cycle of organic dust on Titan, and causing similar effects to those that can be observed on Earth and Mars.

Copyright: IPGP/Labex UnivEarthS/University Paris Diderot – C. Epitalon & S. Rodriguez

ExoMars orbiter prepares for Rosalind Franklin

ZETA, (ESA).- On 15 June, the ESA-Roscosmos ExoMars Trace Gas Orbiter (TGO) will follow a different path. An ‘Inclination Change Manoeuvre’ will put the spacecraft in an altered orbit, enabling it to pick up crucial status signals from the ExoMars rover, Rosalind Franklin, due to land on the Red Planet in 2021.

After completing a complex series of manoeuvres during 2017, ExoMars TGO is now orbiting the Red Planet every two hours, collecting scientific data from NASA’s surface-bound rover and lander, and relaying it back to Earth. At the same time, the orbiter is gathering its own data on the planet’s atmosphere, water abundance and alien surface.

 More than a year before Rosalind even lifts off from Earth’s surface, flight dynamics experts at ESA’s ESOC mission control centre have formulated a long-term plan to ensure ExoMars TGO can communicate with the new ESA rover and surface platform, contained in the entry, descent and landing module.

Slight changes to a spacecraft’s orbit have a large effect over time, so while the upcoming manoeuvres will only slightly alter TGO’s speed, it will be in the right position to communicate with the then-incoming rover by 2021.

Mars’ uneven gravity field means that TGO’s orbit ‘wanders’, so it gradually rotates around Mars over time. As illustrated in this image, the spacecraft first follows the black path, then the green, then the red – continuing until it completes an entire rotation around the planet every four and a half months.

To keep in touch with the descent module as it enters the Martian atmosphere, descends, and lands upon its surface, TGO’s orientation needs to change.

Three manoeuvres in the month of June will alter TGO’s speed, twice by 30.9 metres per second and one final small change of 1.5 metres per second, bringing it slightly closer to the Martian poles.

Thanks to these manoeuvres, TGO’s path will look more like the second graphic shown here, illustrating ‘snapshots in time’ during the 2021 descent of the new rover.

The green line represents Rosalind Franklin’s landing approach path.

The black line shows the TGO orbit with its optimised orientation, two years after the upcoming manoeuvres.

The red path shows TGO’s original orbit.

In February 2021, a small manoeuvre will be performed to ensure TGO is in the right place at the right time for the lander's arrival.

The result of all these manoeuvres combined can be seen in the third graphic.

The black line represents TGO’s orbit around Mars at the time Rosalind Franklin begins descending, shown by the green line.

Blue dots along the orbits of both spacecraft are connected by horizontal lines, illustrating their relative positions at different time intervals, and how they are able to ‘see’ each other at every moment, thus ensuring that radio contact can be maintained.

If teams at mission control were to leave ExoMars TGO in its current orbit, without performing any manoeuvres, Mars itself would later get between the orbiting spacecraft and the new Mars explorer.

In this final graphic, the red line illustrates TGO’s un-phased orbit, and again the green line shows Rosalind Franklin’s entry path and Blue dots represent moments in time for each spacecraft.

Lines between the dots reveal how in this scenario, Mars would block their view of each other.

Without phasing the orbiter with the Mars rover, the two craft will remain invisible to each other at the crucial moment when the rover descends to the surface.

Not only does the foresight and long-term planning of mission experts ensure communication is maintained between two of ESA’s most important Mars missions, it saves fuel – a huge amount of which would be needed to get TGO in the right position in the weeks or even months before the ExoMars rover's arrival.

Follow the progress of ESA’s ExoMars Trace Gas Orbiter on Twitter, here, and Rosalind Franklin rover, here.

ESA has demonstrated expertise in studying Mars from orbit, now we are looking to secure a safe landing, to rove across the surface and to drill underground to search for evidence of life. Our orbiters are already in place to provide data relay services for surface missions. The next logical step is to bring samples back to Earth, to provide access to Mars for scientists globally, and to better prepare for future human exploration of the Red Planet. This week we’re highlighting ESA’s contribution to Mars exploration as we ramp up to the launch of our second ExoMars mission, and look beyond to completing a Mars Sample Return mission. Join the conversation online with the hashtag #ExploreFarther

For 6 Weeks, Mars Will Appear Larger, Brighter to Earth Stargazers

WASHINGTON, (VOANEWS).- Astronomers and stargazers will get a chance to get up close and personal with Mars over the next six weeks, as the Earth passes between the Red Planet and the sun.

Mars will make its closest swing toward Earth, bringing it closer and appearing brighter, than it has in the past 15 years.

In 2003, Mars came within 56.1 million kilometers of Earth, the closest it had come in 60,000 years, according to the Weather Channel.

This year the two planets won't get quite as cozy. The Weather Channel said Mars will appear the brightest to Earth stargazers on July 31, when the two planets are just 57.6 million kilometers apart.

How large Mars appears in the sky to people on Earth depends on where the two neighboring planets are in their elliptical journey. While it takes Earth 365 days to orbit the sun, it takes Mars almost twice as long, or 687 days.

In 2016, the planets were at the opposite ends of their orbits, with 75.6 million kilometers between them, making Mars appear very small.

The next time Mars comes this close to Earth will be in March 2035.

NASA Offers Challenge with $750,000 Reward to Further Mars Goal

WASHINGTON, (VOANEWS).- The U.S. space agency NASA is offering a public challenge, with a lofty $750,000 reward, to anyone who can find ways to turn carbon dioxide into compounds that would be useful on Mars.

Calling it the “CO2 Conversion Challenge,” NASA scientists say they need help finding a way to turn a plentiful resource like carbon dioxide into a variety of useful products in order to make trips to Mars possible.

Carbon dioxide is one resource that is readily abundant within the Martian atmosphere.

Scientists say astronauts attempting space travel to Mars will not be able to bring everything they need to the red planet, so will have to figure out ways to use local resources once they get there to create what they need.

“Enabling sustained human life on another planet will require a great deal of resources and we cannot possibly bring everything we will need. We have to get creative,” said Monsi Roman, program manager of NASA’s Centennial Challenges program.

She said if scientists could learn to transform “resource like carbon dioxide into a variety of useful products, the space — and terrestrial — applications are endless.”

Carbon and oxygen are the molecular building blocks of sugars.

On Earth, plants can easily and inexpensively turn carbon dioxide and water into sugar. However, scientists say this approach would be difficult to replicate in space because of limited resources, such as energy and water.

NASA says the competition is divided into two phases. During the first phase, individuals or teams would submit a design and description of their proposal, with up to five teams winning $50,000 each. In the second phase, the finalists would build and present a demonstration of their proposals, with the winning individual or team earning $750,000.

Those who are up for the challenge need to register by Jan. 24, 2019, and then officially apply by Feb. 28, 2019.

Recent tectonics on mars

BARCELONA, (ESA).- These prominent trenches were formed by faults that pulled the planet’s surface apart less than 10 million years ago.

Cerberus Fossae in context

The fossae – meaning ‘ditches’ or ‘trenches’ in Latin – stretch for more than 1000 kilometres from the northwest to the southeast.

They cut through impact craters and hills along the way, as well as 10 million year old volcanic plains, indicating the relative youth of their formation.

They vary in width, typically from a few tens of metres to over a kilometre wide, and are thought to be tectonic features originating from faults that stretch the upper layers of the surface apart.

They could be linked to injections of lava at depth deforming the surface above, perhaps originating from the trio of volcanoes that are located to the northwest.

Perspective view of Cerberus Fossae

Rounded collapse pits observed in the northern part (north is to the right in the main colour image) indicate an early stage of surface sinking; in other places rounded features can be seen connecting up to create longer cracks.

Scientists studying this region have speculated that the fractures could rupture the crust to a certain depth, allowing lava or groundwater to escape to the surface.

To the west, as seen in the context image, the Athabasca Valles outflow channel links with the fossae system.

Perspective view of Cerberus Fossae

The dark material seen in the largest crater at the north (right) and around some of the cracks is sand blown by the wind across the martian surface.

Mars Express celebrates 15 years in orbit this year, and scientists are discussing some of the mission's highlights at the European Planetary Science Congress this week in Berlin, Germany.

Topographic view of Cerberus Fossae

During its mission lifetime it has taken over 40,000 images of Mars and its two moons with the high resolution stereo camera, as well as context images with its Visual Monitoring Camera. It has also collected a vast dataset with its suite of scientific instruments that are analysing the planet from its ionosphere, atmosphere, and interaction with the solar wind, through to its subsurface with radar.

Explore all available Mars Express data in ESA’s Planetary Science Archive.