The little craft was low enough that its engine was pushing around dust that had lain undisturbed for millions of years, and here were human beings seeing that with their own eyes. Other than Monday, the week here has been devoted to the outer planets, and before I leave that subject, I want to work in the findings of a team of astronomers looking at the early history of the asteroid belt.
5 winter activities you simply can't miss in the Aosta Valley
That points to an early system that, at particular times, underwent upheaval caused by a rearrangement of the gas giant planets. The model proposes that the gas giant planets migrated to their present positions long after the protoplanetary gas disk had dissipated, playing a role in the Late Heavy Bombardment of the inner planets some 3. Image : The asteroid belt lies in the region between Mars and Jupiter.
Credit: Lunar and Planetary Institute. Kleomenis Tsiganis Aristotle University, Thessaloniki notes the evidence for this idea in the asteroid belt, which the team used in its modeling:. Our model allows us to make the case they were hit by captured comets or perhaps their fragments. If so, they are telling us the same intriguing story as the lunar samples, namely that the solar system apparently went berserk and reconfigured itself about 4 billion years ago.
This is a new view of the asteroid belt, one that will need follow-up through studies of meteorites, asteroids and the moon.
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The paper is Levison et al. Europa is unusual enough, but the evidence for that ocean beneath the ice is persuasive. Can we extend the paradigm all the way out to the Kuiper Belt? If so, missions like the Haumea orbiter or probes to other trans-Neptunian objects become imperative.
At the Aosta conference, I had the chance to talk to Joel Poncy after his presentation on the Haumea project, a conversation that led to astrobiology. Poncy referred me to a paper by Steve Desch Arizona State and colleagues discussing cryovolcanism on distant objects like Charon, and making some startling statements about the possibility of liquid water 40 AU and more from the Sun.
Desch looks at the evolution of Kuiper Belt Objects using a model his team constructed that shows how they might retain enough heat to keep subsurface water in a liquid state. We predict that Charon contains a rocky core… of radius km, surrounded by a slushy layer about 30 km thick containing a mix of ADH [ammonia dihydrate] and liquid water and ammonia. Above this layer is a layer of solid water ice… from to km, surrounded by an undifferentiated crust of rock, water ice and ADH, about km thick.
Only about half of the mass of Charon ever experiences differentiation. Our thermal evolution models suggest that within a few x 10 8 yr, the subsurface liquid will freeze entirely. Of course, a few hundred million years is well down the road. The news is that Charon may contain liquid water now.
The paper continues:.
We conclude that objects with a densities similar to Pluto and Triton, 2. Our time-dependent thermal models of KBOs show that it is possible for Charon and Quaoar and many other small KBOs to retain liquid water to the present day. Thus the interesting reflectivity of Haumea, which may well indicate cryovolcanism, a mechanism that should also be at work on objects like Charon as liquid is delivered to the surface. Another world with evidence for water ice is Quaoar.
The paper is Desch et al. The mission, developed conceptually by Thales Alenia Space and presented at Aosta by Joel Poncy, is particularly demanding because this outer system object has no atmosphere. You can make the case for a Neptune orbiter with associated study of Triton, as several readers have already done, but if you want to orbit Haumea, no aerobraking is possible to ease orbital insertion. The Haumea mission, in other words, deliberately pushes the state of the art in both propulsion and power generation.
Poncy noted in his talk at the Hotel Europe that his team had adapted an in-house software model to optimize the propulsion possibilities. They assume a direct trajectory to Haumea with arrival around , when the object is at 49 AU, and they weigh the benefits of a gravity assist by Jupiter to help shorten the journey.
Every nine days Namaka passes directly in front of or behind Haumea as seen from Earth. Taking the hardware to its limits, Poncy and colleagues come up with what looks to be a feasible mission concept, one with a specific impulse of seconds, a launch mass of kilograms and a flight time of about 21 years. Says Poncy:.
This set of parameters corresponds to what should be achievable in a near future, provided that VASIMR and beta-voltaic technologies are implemented into respectively propulsion and power units by adapting their design and operating point to this class of spacecraft. A lot is in play here. For another, Poncy himself notes the problem with generating the power needed to fly this mission. Yesterday I talked about the scientific value of a Haumea mission, but the second motivation for going to this distant object is to use the mission as a technology driver.
A fast journey to an object like Haumea thus becomes a way to extend our science to planetary objects within AU that can at the same time increase our capabilities for reaching Jupiter or Saturn space with the kind of heavy payloads we want to see in operation there. Poncy sees Haumea as a targeting goal for developing the next tools we need as we expand our studies of closer worlds like Europa and Titan.
The paper is Poncy et al. Poncy Thales Alenia Space, France and colleagues have been developing ideas for the extraordinarily difficult challenge of not just sending a probe to the outer system, but slowing it down for orbital capture. Nonetheless, there are solid reasons for thinking about such a mission. The first is purely scientific.
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The first illustration shows the Solar System most of us grew up with, a system with nine planets that were more or less clearly defined, with what was assumed to be a certain amount of debris and cometary material further out. Now, of course, we see a new Solar System. If we now recap all sizable Solar System planetary objects larger than km, we get 19 objects closer than the orbit of Uranus, orbit-able after a decade or so of cruise with current technologies.
Uranus itself can be flown by but not orbited for a decent travel time. We have already more than 40 objects at Uranus and beyond and this number will grow considerably by Consider, too, that we once thought of the the Solar System as being enclosed in a well defined heliosphere that separated it from true interstellar space.
Now we have objects like Sedna, with an aphelion AU that is well beyond the heliosphere. In moving to its perihelion at 76 AU, Sedna moves from interstellar space into the heliosphere and then gradually works its way back out again. The new Solar System is packed with objects that defy all the definitions we once brought to the term. More unusually, rather than being spherical, it appears to be a flattened ellipsoid with its largest axis in the range of kilometers.
5 winter activities you simply can’t miss in the Aosta Valley
Image : Relative sizes of the larger outer system objects. Note the ellipsoidal shape of EL61, now known as Haumea. Feild STSci. The current thinking is that Haumea is the result of a major collision, one that produced the entire system of TNO and two moons. Adding to the interest is that Haumea is quite reflective, its surface covered with crystalline water ice. This could be interpreted as evidence for cryovolcanism think Triton , and brings home the usefulness of an orbiter. The only thought that drives me out of the room is that I want to do at least a little bit of sports.
I can imagine what will await me later in the evening in the restaurant and so I make at least a few rounds in the hotel pool in the spa before I plunge into the next culinary adventure. I want to stay here! At the base of the surrounding mountains there are terraced vineyards. Here and there a castle towers on a top of a hill above the valley. Only a handful of villages are grouped against the snow-capped three and four thousand metre peaks.
The town of Aosta lies at metres above sea level. The cosy small Italian town with its 35, inhabitants could not have found a more beautiful setting. Besides pretty shops and restaurants, you will find many traces of an eventful history from Roman times to the present days. From the Augustus Arch to the ruins of the Roman theatre. During Christmas time, small wooden houses populate the square next to the Roman theatre, where local delicacies and handicrafts are sold.
I can barely imagine a more beautiful place for a Christmas market. And again I plan to come back with more time next time. With much more time. A real fairytale castle with many towers and elaborate frescoes. The origins of the castle date back to the 13th century and it has been continuously extended over the centuries.
With sunny regards,. Therefore I would recommend a travelling here by car. This has the advantage that it is also unbound in the area.
It is very worthwhile to actively discover the Aosta Valley. From Zurich the drive by car to Aosta takes about 4 hours and 30 minutes.