The first science findings from NASA’s Juno mission were published at the end of May 2017, revealing Jupiter to be far more complex a world than had been previously envisioned.
The Juno mission hopes to answer many questions about Jupiter – the structure and composition of its atmosphere, a greater understanding of the forces driving that atmosphere and the distinctive upper layer cloud formations, its magnetic field, weather patterns, and so on. It is also hoped the mission will resolve the question of what actually lies at Jupiter’s core.
Two theories have tended to dominate thinking around the latter: that Jupiter either has a relatively compact solid core 1 to 10 times as massive as Earth or it has no solid core at all, just gases compressed to a liquid state. However, the data returned by the spacecraft since it arrived in orbit around Jupiter in July 2016 doesn’t support either hypothesis. Instead, it suggests Jupiter has a large, partially dissolved core of ices and rock.
This conclusion comes via measurements of the magnitude planet’s magnetic field, which has not only proven to be significantly higher than expected, but also exhibits large spatial variations, being significantly higher than expected in some locations, and markedly lower in others. These results suggest that Jupiter’s core has a molecular hydrogen layer which appears to be the dynamo layer driving Jupiter’s magnet field, sitting over a metallic hydrogen layer which gradually transitions into a “fuzzy core” of ices and rock.
The Juno data also suggest the turbulent “meteorological layer” of Jupiter’s atmosphere, where the familiar bands of cloud exist, extends downwards more than 1,000 km (625 mi), with the tropical zoning of banded cloud layers extending down to pressures of up to 100 bars – or 100 times Earth’s air pressure at sea level), before transitioning to slightly less turbulent regions.
It had been thought that somewhere beneath the cloud layers the gasses present in the atmosphere would be more well mixed. But again, the Juno data suggests otherwise. “We’re finding that that’s just not true at all,” Dr. Scott Bolton, Juno’s principal investigator said as the first set findings was published on May 25th. “There’s structure down deep, but it doesn’t seem to match the zones and belts. And so we’re still trying to figure it out.”
“What we’ve learned so far is earth-shattering. Or should I say, Jupiter-shattering,” he also stated. “Discoveries about its core, composition, magnetosphere, and poles are as stunning as the photographs the mission is generating. Juno is re-writing all we thought we knew about Jupiter.” It is also adding new mysteries to Jupiter’s story as well.
One of the most remarkable aspects of the Juno mission so far have been the amazing images of the planet’s north and south polar regions. Rather than being banded, as with the rest of the atmosphere, or uniformly regimented into a geometric form, like Saturn’s north polar region, the atmosphere over Jupiter’s poles is a chaotic mix of swirling cyclones and storms, some of them 1,400 km (870 mi) across, towering bove the bluish backdrop of Jupiter’s deeper atmosphere.
“it’s ‘s unclear what, exactly, drives these polar cyclones,” Bolton states. “Over the course of the mission, we’ll be able to watch the poles and see how they evolve. Maybe these cyclones are always there, but maybe they just come and go.”
Juno has also suggested the cause of Jupiter’s auroral displays might be more complex than previously thought.
Earth’s auroras result when the solar wind — charged particles streaming from the sun — are funnelled by the planet’s magnetic field to slam into the atmosphere over the north and south pole in a complex two-way interaction which results in the glow of the northern and southern lights.
It had been thought to be the massive flux tube linking the polar regions of Io, Jupiter’s innermost Galilean moon, and Jupiter’s own polar regions was the driver of the planet’s auroral displays thanks to the 5 million ampere electrical current flowing through the flux. However, data from Juno, which has been combined with observations from Japan’s Hisaki satellite and the Hubble Space Telescope suggest the gases spreading outward from Io as a result of its extreme volcanism, undergo a complex interaction with the “shock wave” formed by the solar wind as it strikes the outer limits of Jupiter’s massive magnetic field.
This interaction deflects energy from the gases back towards Jupiter at velocities of between 400 and 800 kilometres a second (250 and 500 miles per second). When this energy strikes and penetrates Jupiter’s atmosphere, it gives rise to bright, transient aurora. In addition, it is being theorised that this energy, when it reaches icy Europa and Ganymede – both of which are thought might harbour basic life in the oceans beneath their icy crusts, could provide support for chemical processes on their icy surfaces. This is liable to be something scientists will be considering carefully as more data from Juno is scrutinised.
Tabby’s Star: New Theory
In my previous Space Sunday report, I again wrote about “Tabby’s Star” – more correctly, KIC 8462852. An F-type main-sequence star located in the constellation Cygnus approximately 1,480 light years from Earth, it undergoes irregular dips in brightness over the course of several days and some of which can see it dim by up to 22%, before it reverts to its “normal” brightness once more. Explanations for this dimming have been wide-ranging, encompassing everything from natural stellar phenomena to gigantic alien structure orbiting or partially enclosing the star.
As I note, a world-wide alert was sent out in mid-May, when it appeared Tabby’s star was starting on a major downward swing in brightness, marking it an ideal time to study it in an attempt to better understand what might be causing the dimming. Now a team of scientists and astronomers from University of Valencia, the Institute of Physics of Cantabria (IFCA) and the Astrophysical Institute of Andalusia (IAA) have put forward a new possible explanation.
Using data from the May 2017 dimming and known prior events, they have built a model which explains the dimming in terms of natural phenomena. They propose that orbiting “Tabby’s Star” a massive planet, perhaps 1/3 the radius of the star, which has an extended ring system, perhaps 5 times the diameter of the star around it, inclined by 5-degrees. Sharing the planet’s orbit around “Tabby’s Star” at the L4 and L5 positions in front and behind the planet, are two truly massive stable clouds of Trojan asteroids.
Such a model accurately account for both the irregular large-scale dimming of the star’s brightest (by up to 22% at a time), the non-periodic repetitions and asymmetric dips in brightness which occur.
However, the model relies on several elements which could be considered contentious. For one thing, KIC8462852 is half as big again as the Sun – so a planet with 1/3 of its radius is going to be huge (Jupiter, for example, only has 1/10th the radius of the Sun). Equally the clouds of Trojan asteroids at the planet’s L4 and L5 points are going to be massive – each potentially equal to the mass of Jupiter. So it is hard to see how these clouds of asteroids could remain stable without being perturbed by the planet’s gravity, or how they’d remain stable within themselves.
Nevertheless, the theory is an interesting one, because not only does it present a natural cause of the dimming which could be possible – it predicts when the next large-scale dimming of “Tabby’s Star” will occur: 2021. If all else fails in our attempts to understand what is going on with this strange star, this prediction will at least serve to prove this theory right or wrong.
The Building Block of Organics and Life
Methanol is a key building block for the complex organic compounds that comprise life. Now, for the very first time,it has been detected in the proto-planetary disk of a relatively young star about 170 light years away.
TW Hydrae, roughly 80% of the Sun’s mass, is roughly 5-10 million years old. It, and the disk of material surrounding it, offers an approximation of how our own solar system may have looked very early on in its development. The methanol appears to be located in a ring peaking at some 30 astronomical units from the star, and its discovery is important as finding it could help scientists better understand the chemistry which might occur during a planet’s formation which might ultimately lead to the emergence of life.
The gas most likely originates from the sublimation of methanol ice within the disk. It is one of the largest complex organic compounds detected in a proto-planetary disks to date, and as more complex organic compounds use it as a basic building block, it might indicate these are also present in the disk, presenting us with an indicator of the amounts of organic compounds that may exist within the icy, comet-forming material orbiting stars.
Here on Earth, it is believed that comets contributed some 9or all) of the organic compounds needed to initiate life here. Thus, the presence of organic-rich comets in the disk around TW Hydrae or other stars could demonstrate that the basic ingredients for initiating or driving life are common within the young proto-planetary systems of the galaxy.
Quick Spaceflight Round-up
Kiwis In Space!
Rocket labs, a New Zealand based company aiming to enter the lucrative small satellite / payload market (150 and 225 kg / 330 to 496 lbs), successfully completed the first test launch of its Electron rocket on Wednesday, May 24th.
Built entirely in-house by the company – including its rocket motors – the two-stage Electron lifted-off at 16:20 local time (05:20 UT) from the company’s launch complex on New Zealand’s North Island Mahia Peninsula, successfully testing the launch, separation and second stage motor firing for the vehicle.
The small payload market is one of the fastest growing commercial space sectors. However, launches are complicated as small payloads generally have to “hitch a ride” aboard big, expensive rockets like the Falcon 9 as they launch much larger payloads into orbit. Rocket Labs hopes that the small, relatively inexpensive Electron will be seen as a low-cost, no waiting launch service to those otherwise reliant on “piggybacking” their payloads on larger launches.
A unique feature with the vehicle is its “plug-in payload” fairing. This can be delivered to customers, allowing them to install their payloads into the fairing and then seal it so it can be returned to Rocket Labs and then integrated into a launch vehicle. This eliminates the need for customers with environmentally sensitive payloads to risk exposing their equipment to environmental conditions outside of their control prior to installation into the rocket’s payload fairing.
Boeing Get DARPA XS-1 Project Phase II
Follow my previous Space Sunday update, the US Defence Advanced Research Projects Agency (DARPA) has awarded Phase 2 of its Experimental Spaceplane 1 (XS-1) programme to build a reusable space vehicle capable of delivering payloads of up to 2,300 kg (5,000 lb) to orbit at an operational cost of around US $5 million per flight.
The contract, which will comprise development of the vehicle and ground tests though 2019, has been awarded to Boeing. US $146 million in development funding will be provided by DARPA, with Boeing providing the rest of the funding. A third phase of the programme, subject to additional funding, will commence in 2020 and involve 12-15 flights of the vehicle, ensuring it can meet a further requirement of the project: to launch, recover, refurbish and re-launch the XS-1 in a single 24-hour period.
The XS-1 is designed to launch vertically and land horizontally, just like the space shuttle. Although Boeing were awarded the contract, they will not be continuing their partnership with Blue Origin in developing the XS-1. Instead, Aerojet Rocketdyne will now provide the motor system for the vehicle. This will be a modified version of the Space Shuttle Main Engine (SSME), designated the AR-22, and so will be something of a cousin to the RS-25 engines which will power the core stage of NASA’s Space Launch System rocket.
Sierra Nevada Pass Key NASA Milestone
Sierra Nevada, the company behind the Dream Chaser “mini-shuttle” (see here, here, here and here) has passed a further milestone in their plans to become the third US company to carry out cargo missions to / from the International Space Station (ISS). On Thursday, May 25th, it was confirmed the uncrewed version of the Dream Chaser vehicle, designated Dream Chaser Cargo, had successfully passed its third integration review, indicating it can meet NASA requirements for transporting cargo to and from the space station.
If all continues to run to plan, Dream Chaser Cargo will commence flying resupply missions to the ISS in 2019.