Hot answers tagged

106

(*) Jupiter, for all intents and purposes, doesn't have a solid surface to stand on. Not any more than you could say that Earth's atmosphere has it, before you hit Terra Firma. It's an enormous ball composed of mostly Hydrogen and Helium, but also other heavier elements in smaller parts, and it's so massive that its own gravity compresses these gases into ...


53

As @Hobbes mentioned it is not an image of an entire hemisphere but it has been distorted to allow for wide angle vision. That's why it looks so strange. The image is a composite made by Kevin M. Gill (a software engineer from NASA's JPL) using the JNCE_2019255_22C00023_V01, JNCE_2019255_22C00024_V01, JNCE_2019255_22C00025_V01, JNCE_2019255_22C00026_V01, ...


48

The speculation is that Galileo gradually sunk into thicker layers of Jupiter body, and eventually reached level where pressure squeezed its RTG battery so much the plutonium went supercritical. Galileo was powered by RTGs. That is a heat source powered by the decay of Plutonium-238. Nuclear decay rate does not change. It isn't affected by pressure, ...


45

Jupiter being a gas giant is not about its appearance, as another answer stated. It's only about the mass distribution of a planet. Jupiter's mass is 320 Earth masses, while we know from the Juno mission that the rock/ice in the core account for 5–25 of these Earth masses. So the rest of about 300 Earth masses is gas. Thus Jupiter is a gas giant. It is ...


30

The Galileo probe carried two radionucleid batteries, each one carrying 7.8kg of Plutonium-238. But Plutonium 238, while radioactive, is not the kind of Plutonium used for nuclear bombs. That's another isotope: Plutonium-239. That's a big difference, because only the kinds of Plutonium with odd isotope numbers are fissile. Fissile means, that they are ...


23

It was said in here that the time to reach Pluto was shortened by 3 years. It's also said that after the Jupiter flyby the probe gained ~ 4 km/s accelerating to the speed of 23 km/s relative to the Sun. We can use simple Keplerian estimate (ignoring all complexities of the actual orbital mechanics) to obtain the speed when the probe approaches Pluto, \begin{...


22

While many missions have been able to continue beyond their design lifetimes (Cassini and the Mars Exploration Rovers being prominent examples), the type of mission and orbit Juno must undertake to accomplish its goals will subject the spacecraft to a truly massive radiation dose. In order to meet the mission’s science goals within the budget set by NASA, ...


22

Yes, it absolutely would! The radiation on Europa is about 5.4 Sv (540 rem) of radiation per day. Looking at this guide, and assuming you want to meet OSHA standards of 5 rem per year, you would need to only allow 1 part in 40,000 of the base radiation to make it through. The website linked indicates you want a mass of about 375 pounds/square foot to only ...


20

Using NASA's Eyes measuring the distance from Jupiter to Earth at this moment (5th Jul 2016, 11:50 CEST) is 48 light minutes, 21.39 light seconds, and that would be the time Juno's communications take to reach Earth.


19

Could they be harvested? Sure. Could they be harvested in an economically profitable way? Probably not, for all the reasons you listed. There's a lot of unknowns to this question — while the chemistry they mention certainly makes sense, there's lots of stuff about the atmosphere we don't know. A harvesting ship would need to find exactly what ...


18

JunoCam used different technologies than does the typical framing camera one buys at a store. A typical digital color camera uses a Bayer filter pattern, a row of alternating tiny blue and green filters, followed by a row of alternating tiny green and red filters, each filter covering a pixel, followed by a row of alternating tiny blue and green filters, and ...


18

Let's go back our old friend the Pork chop plotter. Earth to Jupiter using minimum fuel takes around 2 years and you get one opportunity per year, more or less, to get there. You can shorten the journey to perhaps 20 months with minimal extra fuel. The delta-V required at Earth (over and above escape velocity) is about 9.3 km/s (you can in theory aerobrake ...


16

EDIT: based on @Beska's comment, I went back and calculated the difference including light time. In other words, you have to use Jupiter's position roughly 48 minutes ago to state the travel time. Using the observe() method, which does this, there is a difference of 0.02 seconds. This doesn't really matter, considering that Juno is in a large orbit around ...


15

This paper describes the Juno telecomm system in detail. It is a standard deep-space X-band system with a 2.5 m high-gain antenna, a 25 W traveling-wave tube amplifier, and concatenated convolutional and Reed-Solomon or Turbo 1/6 rate error-correcting codes. It will get 18,000 bits per second down to a 34-m antenna on Earth at maximum range (6.459 AU) at a ...


15

From the Yellow Book: "06/2022 - Launch by Ariane-5 ECA + EVEE-type Cruise" EVEE means Earth Venus Earth Earth - a long series of gravity assist maneuvers to fit more payload into the Ariane 5 ECA launcher capabilities. Why an Earth slingshot comes first: The fact that the first arc includes an Earth gravity assist for both launch opportunities ...


15

If you saw the video of the Shoemaker-Levy collision you will see that although that was a collection of smaller objects, there is very much a collision, rather than a gas engulfing a solid. Once the object gets within Jupiter's Roche limit it will be torn to pieces, so you will have a hail of objects falling in and burning up through the atmosphere. The ...


15

One reason they are called gas giants is because they are mostly composed of elements that are gaseous at Earth like temperatures and pressures. Jupiter is primarily composed of hydrogen with a quarter of its mass being helium, though helium comprises only about a tenth of the number of molecules. Jupiter's upper atmosphere is about 88–92% hydrogen ...


13

For Jovian and Saturnine moons, the simplest answer is no, at least not much more habitable than our own Moon is, because none of these moons have their own magnetic field or sufficient mass and their atmosphere would eventually thin out via the ionospheric hydrogen loss due to the solar wind. A bit more difficult answer is how many of these moons would be ...


12

No, the Atlas 551 is not powerful enough to send Juno to Jupiter. From this article on NASA's website: The Juno spacecraft was launched from Kennedy Space Center in Florida on August 5, 2011. Juno’s launch vehicle was capable of giving the spacecraft only enough energy to reach the asteroid belt, at which point the sun’s gravity pulled it back ...


12

Acceleration due to gravity is given by $$ a = \frac{GM}{r^2} $$ where G is the universal gravitational constant, M is the mass of the central body and r is the distance between the bodies' centers. For Jupiter at ~5.2 AU average orbital radius, this works out to 0.22 mm/s$^2$. This is $2.2\times10^{-5}$ (or 0.000022) times the gravitational acceleration ...


12

A Europa lander would need much more shielding, and/or more radiation tolerant components. Juno's orbit avoids the main radiation belt, but Europa is right in the middle of it.


12

Voyager was continually pointing its camera towards Jupiter, while passing alongside it, with its closest approach being 349,000 km. With no visible fixed references behind the planet, it's not obvious that the camera direction is changing during the approach.


11

You won't see Jupiter's atmosphere from the "inside". The entry and destruction of the vehicle is very fast, and occurs relatively high in the atmosphere. Way, way above any clouds. There would not be time to take an image, process it, and get it out the antenna, even if you happened to have Earth in view for the entry. Even if you did have a picture looking ...


11

There's an interesting Planetary Society article about this: What to expect from Junocam We won't be able to see spectacular views of Jupiter's belts and zones from Jupiter orbit until the very end of August, and it'll be November before we'll see automated release of high-resolution raw images. August 27 is expected to be a day when photography takes ...


11

Jupiter is about as large as a planet can get, physically. Suppose we slowly add hydrogen and helium to Jupiter, so slowly so as to keep it at more or less its current temperature. Surprisingly, it would get smaller. Jupiter is about as large as a planet can get. (There are exoplanets that are larger than Jupiter, but that's because they orbit so close to ...


11

Depending on the time of launch, there were 4 different major plans for the NH mission profile. The first 3 involved Jupiter flybys, and would have an arrival date of 2015, 2016, or 2017. The last was a direct flyby, which I believe would have been 2019-2020, per this article (. As for the scientific value, going slower through the system would have ...


11

No, there are no planned missions using an Ion drive to the outer solar system. The reason is something that you haven't taken in to account. Sunlight drops significantly as one goes further from the Sun. One might be able to get the continuous acceleration you indicated to get to the Asteroid belt, but to go much further then that would require large solar ...


11

I whomped up a spreadsheet to compare scenarios like this: Hohmann.xls. Typing Earth into departure planet cell and Mars into destination planet I get Launch windows open each 2.14 years (synodic period) Trip time .71 years Delta V Low Earth Orbit to Low Mars Orbit: 5.7 km/s Typing Mars into departure planet and Jupiter into destination: Launch window: ...


10

Deer Hunter's covered JUICE's flight itself, so I'm limiting my answer to Addressing why New Horizons and Cassini were so much faster. There is a defacto upper bound in how long it can take for a probe to reach its destination because the scientists who do all the work to design and build a mission also want to be around for the payoff when it arrives. ...


10

According to NASA's NH Jupiter press kit: Closest approach was on February 28, 2007 Download began on March 14 After the Jupiter encounter, the first hibernation mode cycle started on June 28, 2007. On May 1, 70% of the data was downloaded. At that rate, it'd take 8.5 weeks to download the full data set. About 70 percent of the expected 34 gigabits ...


Only top voted, non community-wiki answers of a minimum length are eligible