Ignoring all the fascinating stuff about Jupiter, let me point out this gem: The download of six megabytes of data [...] took one-and-a-half days
I sometimes like to scare kids by telling them about the time when I surfed the Internet with 14.4 kbit modem, but even that looks incredibly fast compared to the speed of interplanetary data transmission (back then, 6 MiB would have taken me about 2-2.5 hours).
(NB that I am not complaining or anything, just pointing out that this is many orders of magnitudes slower than anything one would normally consider a "slow" connection.)
> On the HGA we expect ≥18 kilobits per second (kbps) (≥12 kbps during Grav passes due to power required for carrier signal), and ≥10 bps on the MGA.
HGA = High Gain Antenna, MGA = Medium Gain Antenna. HGA activity is limited to when the spacecraft is precisely aligned towards Earth:
> Due to the nutation of the spinning spacecraft following any maneuvers, we will need to allow several hours for nutation damping following Earth-point maneuvers before using the HGA.
> Currently we allow 8 hours prior to most DSN tracks and 16 hours prior to the 6-hour MWR or Grav perijove science passes that start at PJ – 3 h.
So it's not necessarily any slower than your modem once it gets going, it just has terrible latency and dialing the connection can take the better part of a day.
That means when humans finally colonize Mars, there will be two FaceBooks, FB Mars and FB Earth, with any communication between them running at a lag.
I bet there will be AI research to create bots to act in "real time" on your behalf on the opposite planet. If the artificial agent can imitate your own actions and judgements, it would be a good way to surpass the speed of light. It will be necessary to build these agents because other interested parties could use the time lag to unfairly gain an advantage over you. The more we explore, the larger the time lag. With Jupyter it is 33-53 minutes. With Pluto it's 5h. The nearest star - 4 years. The Moon is at 1.3s.
It seriously sounds like you might have a notification addiction: you should try forcing yourself to check messages at most only a few times a day for a while to detox.
Distributed systems are hard to get correctly when there's a few extra milliseconds of latency. Imagine now having 30 minutes of latency be the norm, and sometimes more.
It's an interesting problem I hope I'm around to witness.
This is off topic for this post, but astronomy, space and space missions always have a way of putting things in perspective and showing how much humans have progressed and learned, and also the magnitude of human achievement (in the past) with what seem like completely unusable equipment today.
I look at the Voyager (1 and 2) data whenever I feel like comparing things to what we have today, and I always end up being overwhelmed by the facts, figures and what humans have achieved. I can't help but be awed.
Quoting from the Voyager FAQ [1]:
> Question: How fast are the Voyager computers?
> Answer:Not very fast compared to today’s standards. The master clock runs at 4 MHz but the CPU’s clock runs at only 250 KHz. A typical instruction takes 80 microseconds, that is about 8,000 instructions per second. To put this in perspective, a 2013 top-of-the-line smartphone runs at 1.5 GHz with four or more processors yielding over 14 billion instructions per second.
Quoting from the Voyager Interstellar Science page [2]:
> Science data are returned to earth in real time at 160 bps.
Just imagine sending data to earth at 160 bps from a distance of 20 billion kilometers and 17 billion kilometers^ [3] , respectively, for Voyager 1 and Voyager 2. The time it takes light to travel between earth and Voyager 1 and Voyager 2 is currently about 19 hours and 15.5 hours^, respectively. (Some other communication is collected and sent at 115 kbps)
^: These figures are rounded since it doesn't make a huge difference to me at this magnitude, and also, the distance from earth to these two spacecraft does sometimes decrease due to earth's revolution around the sun.
> Just imagine sending data to earth at 160 bps from a distance of 20 billion kilometers and 17 billion kilometers^ [3] , respectively, for Voyager 1 and Voyager 2.
Sending data - regardless of bandwidth - over these distances is very impressive in my book. Let alone sending a computer so far and have it still work after all these years.
“Saturn has a hexagon at the north pole,” said Bolton. “There is nothing on Jupiter that anywhere near resembles that. The largest planet in our solar system is truly unique. We have 36 more flybys to study just how unique it really is.”
Does Saturn have an identical cloud pattern on its south pole? I always hear about the north pole, but without geographic features wouldn't there be symmetry between the north and south poles?
"This is the first I've heard of Saturn's hexagon, very interesting"
Yes, me too -- thanks for posting your reply and the link, I've now learnt something new today (and it's only 00:45 so that's a good start to the weekend!).
Saturn has a tilt just a bit more than the Earth and it experiences seasons; the pole is rotated something like 26 degrees into our field of vision in "winter". Uranus is actually rotating on it's side.
The answer is we don't. Unlike the other three gas giants in the Solar System we can't see Jupiter's pole clearly. So Jupiter is unique to our solar system, and we don't know much about the visual details of exoplanets.
The thing is, there's a lot of gas, which like any other matter, has mass. So, even though a hydrogen atom is the lightest element possible, and we think of hydrogen gas a being light, that's just relative to other things. At a human scale, it isn't possible to have that much of the stuff around. But you can always go and collect a lot of it; in fact if you get ten to the power twenty seven kilograms of the stuff, and put it in one place, gravity will shape it into a sphere that looks very like Jupiter. Or, get 1000 times as much as that, and watch as gravity squeezes it so much it begins to fuse into helium at the centre - you'll have a star the size of our Sun...!
Jupiter is almost all hydrogen. However, the bulk of that hydrogen is actually liquid. Its core has compressed the hydrogen so much that it's ionized and is essentially a metal.
It's an interesting story with an awkward headline and opening quote. The word "unique" is being pressed into duty as a terse synonym for "interesting in all sorts of ways that will require you to read entire paragraphs of information to understand."
I'm inclined to forgive NASA on this one. The accuracy/brevity trade-off tortures anyone who tries to popularize science.
It's unique within our solar system, the only one we have details about. I think it's fair to state that as being unique. The implication (that we don't know about other solar systems) doesn't need to be stated, at least to me.
Since we're in the business of nitpicking – unique means one of a kind, so the "truly" is redundant. That said, there are so many planets in the Universe that it's practically impossible for any single one to be unique – the term is being used here not in a technically accurate way, but in a loose, "I want you to be impressed" sense.
Interesting that they phrase the headline almost as if to imply uniqueness. My impression was that Saturn's hexagon was the unique situation (occurring, hypothetically, only under very specific conditions). Is it expected then that Uranus and Neptune's poles will look different still?
I wonder if the clouds don't separate into bands as much at those latitudes because the velocity (due to the planet's rotation) is lower closer to the poles.
The Coriolis force is strongest at the poles and weakest at the equator, so I presume there would be more rotation and thus less banding near the poles due to this effect.
The origin of the banding is supposedly similar to the banding on Earth, which has three broad 'bands' driven by Hadley cells (polar, mid-lattitude, tropical), driven by convective heating moving energy away from the equator towards the poles, except presumably Jupiter has much more energy and therefore more convection and more bands.
I only have a very crude understanding of atmospheric forces, though, so paging someone who knows better.
"The download of six megabytes of data collected during the six-hour transit, from above Jupiter’s north pole to below its south pole, took one-and-a-half days."
The solar panels that Juno has produce only 500 watts of power. You would need a lot more then that to be sending gigabytes of data in any meaningful timeframe. So yes it really is just six megabytes of data taking 30h+ to download. Btw the panels would produce 14kW at earth orbit but suns power goes down quite fast as you move away from it. Also the farthest from the Sun we've ever used solar panels. Traditionally missions this far from the Sun have used some kind of a nuclear power source (RTGs). Though I don't think they could produce 500 watts without being very big.
Transmission is one thing, but collection is another: did they really only collect 6 megabytes of data over the course of a 6 hour flyby?
Off topic, ish: does anyone know how large a solar panel array would have to be to supply all of our current energy use, if the array orbited the Sun at the same distance Mercury does?
According to Wikipedia, the world's average energy consumption is 12.3Tw. Given that the Earth is gets 1366 W/m² of solar power at 149,597,870km, this means Mercury gets 9190 W/m² at 57,910,000km. Plugging these together, this tells us that a 12.3Tw solar array of 100% efficiency in Mercury's orbit would have a surface area of 1338 km².
Realistically, you'd at least double that, to produce the same power, as solar panels are <50% efficient.
Nitpick, the farthest distance of Mercury from the Sun on its orbit is closer to 0.46 AU and it spends most of the time there, so for safe estimate it is better to take this greater value for planet-Sun distance. I get around 100x100 km collecting square near the Earth and almost 50x50 km near the Mercury. Taking into account efficiency and design constraints, it's safer to estimate more like 200x200 km near the Earth and 100x100 km near the Mercury. Clearly, building this near the Mercury brings little benefit as opposed to building it near the Earth. If we built this on the surface of the Earth (seems cheapest, even if the area would have to be quadrupled due to night and atmosphere) it does look practically achievable in the future. Solar energy could sustain current consumption of the human civilization. Most alternative sources of energy are not rich enough to supplant nuclear energy. Solar energy seems to be the best contender.
Then we could beam the energy back to earth using lasers so bright that they would burn plasma holes through our atmosphere and precisely target receiving stations where they would vaporize water which would power a steam turbine. Totally doable, I'd say we could get it up and running in a couple years.
This sounds like sarcasm, but yes: solar collectors in close orbit around the sun, huge flying parabolic mirrors focusing solar energy that's already 7-10x more dense than it is at 1 AU, beaming that energy to receivers sitting in orbit around the Earth (perhaps at Lagrange 1 and, via L4/L5, L2 to reach the night side of the planet), relayed in to near earth orbit satellites, and being beamed down to many surface locations at safe intensities that might well be used to boil ocean water, driving steam turbines and producing fresh water (and salt).
Such a system could provide energy dense power to the entire solar system (skipping the steam turbine step for most locations, and going pure solar electric), up to large installations for entire planets, and down to individual spaceships.
I'm not suggesting we'll do it tomorrow. But within a hundred years, if we get and keep our shit together..?
Short answer: you can't. The Earth's rotation would make collecting that energy very unwieldy. Individual collectors could act like capacitors, but getting that power down to the planet continuously isn't really doable with any current technology.
You wouldn't beam energy directly from near-solar orbit to the surface of the Earth; you would relay it to orbiting receivers around the planet, which would in turn beam it to the surface, and reaching the night-side as well as day-side.
As soon as somebody figures out how to get the energy from the panels back to earth? Assuming we figure out how to economically put them there in the first place...
The cost would be astronomical, I do not think it would be worth it. Much better to build this here on Earth, only 4x more panels needed, still easier to build and maintain.
You don't need to be concerned about Mercury's day unless they're on the surface, essentially. You do need to be concerned with the earth's, and their positions relative to the sun.
In the era of big hard drives and fat pipes, people forget that 6 megabytes is a lot of raw data if it's not packed with unnecessary GUI elements, high-res video, and inefficient code.
Almost all of the instruments on Juno are non-visual. The camera was included mostly for PR purposes. 6MB is pretty good for one-dimensional data streams.
Googling suggests that global energy usage is estimated to be around 15 terawatts.
Using the most efficient multi-junction solar cells available - which can convert 30% of the light hitting them into electricity - we could generate that with about 6.5 million km² of solar panels: that's about 80% of Australia.
Out at Earth's orbit, it'd need to be 68 million km^2: about the area of the Indian Ocean.
I only get (15E12/1360/0.3) = 37 billion m², which is 190x190 km square or 36000 km². Little more than Taiwan, which looks as quite a little spot compared to the globe: https://en.wikipedia.org/wiki/Geography_of_Taiwan
When I was looking into Forward Error Correction a while back all of the impressive stuff was for downlinks from remote space probes.
I don't know any specifics around the Juno probe however most of the techniques usually sent 2-3x the amount of data actually downloaded because a missed frame was 1.5hrs(43mins @ Speed of light from Earth->Jupiter). Being able to reconstruct a frame with redundant data was critical.
Combined with a low power transmitter 6mb is pretty reasonable.
> “Saturn has a hexagon at the north pole,” said Bolton. “There is nothing on Jupiter that anywhere near resembles that. The largest planet in our solar system is truly unique. We have 36 more flybys to study just how unique it really is.”
Eh? Jupiter is 'truly unique' because it doesn't have an extremely puzzling feature that only one other planet is known to have?
Why are people getting bent out of shape about the word "unique"? It is unique because Jupiter has features that we have not observed on any other planet, some of which are mentioned in the article (different types of storm systems, high altitude clouds casting shadows etc). From context, he is clearly not only talking about Saturn's hexagon. This pedantry is ridiculous.
People are confused. As was I at first. Considering the emphasis "truly unique" I expected more treatment of that point by the article. By not having that I was left feeling like I missed something / confused. People generally don't like feeling confused.
Personally, I don't understand the people defending the usage here. As far as I have experienced in my life, when people say "unique" in good faith they mean "one of a kind" and those people who don't use it that way are considered to have done a bait-and-switch.
That said, perhaps there's been a lingustic shift I haven't yet noticed.
> "One of the most notable findings of these first-ever pictures of Jupiter’s north and south poles is something that the JunoCam imager did not see."
No, the article is actually saying that the lack of a hexagon is important. Combined with such insights as "some clouds are higher than other things", the mentioned items really don't add up to a breathless "truly unique". The things we already knew about Jupiter - the vibrant bands and the red dot as obvious starters - are far more interesting and worthy of a discussion about what makes the planet unique.
It's clickbaity. People who already find a topic fascinating will skip right past it and not understand why other readers will bother to complain about clickbait.
There are several sources of heat on Jupiter but the one being studied by this mission is the result of the very large magnetic field around Jupiter's generating auroras that are several times larger than the diameter of Earth.
[edit] Original statement wasn't completely accurate, as it does study the auroras, but they are generated by the planet itself. The solar wind doesn't reach the atmosphere of Jupiter.
The lower theoretical threshold for a brown dwarf star, which fuses deuterium->lithium, is 13 times the mass of Jupiter. There isn't enough mass for fusion to occur on its own no matter how energetic the particles are.
I sometimes like to scare kids by telling them about the time when I surfed the Internet with 14.4 kbit modem, but even that looks incredibly fast compared to the speed of interplanetary data transmission (back then, 6 MiB would have taken me about 2-2.5 hours).
(NB that I am not complaining or anything, just pointing out that this is many orders of magnitudes slower than anything one would normally consider a "slow" connection.)