Why is it so difficult to get to Uranus? The strangest planet
Uranus is the only planet tilted; because of this,
one of its poles is always pointing at the sun and the other in the opposite direction;
this makes it one of the strangest planets and, at the same time, one of the most unexplored.
Why have we done so little to explore this planet? Let's start!
Uranus is the seventh planet in the solar system, the third largest,
and the fourth most massive. It is a gaseous planet that has no surface where humans can walk.
For years, space agencies, in space to NASA have sent various exploration probes
to investigate the solar system's planets. Still, it seems that every time new missions
are proposed to the planets, Uranus passes completely from being perceived, in fact,
is ignored more than its farthest twin Neptune. To date, only one exploration probe has visited
this planet, and it was Voyager 2 that quickly passed close to
it in 1986 solely to gain momentum. So why is there so little interest
in exploring this planet? Is it so difficult to reach, or does it simply have nothing to offer us?
The rarest of all Despite its bad reputation
and few exploration missions, Uranus is not a boring planet at all. On the contrary, it is
one of the strangest and most exciting planets. With a volume 60 times that of Earth, this planet
has a compressed mass of toxic gases. Uranus is similar in composition to Neptune because
the two are different from the other gas giants (Jupiter and Saturn). Because of this, astronomers
sometimes classify them into a different category than what they call the icy giants.
Uranus' atmosphere, although similar to Jupiter and Saturn which is composed mainly of hydrogen
and helium, contains a higher proportion of "ice" and water, ammonia, and methane,
along with traces of hydrocarbons. It has the coldest planetary atmosphere in the solar system,
with a minimum temperature of 49 K (-224 °C). It also has a very complex cloud structure,
arranged by levels, where it is believed that the lowest clouds are composed of water and
the highest of methane. In contrast, Uranus' interior is composed mainly of ice and rock.
Because of this, Uranus does not have a solid surface; in fact, none of the gaseous planets have
it. There are no definite limits, nothing to stop or sail on, just a mixture of gases and liquids
that continuously mix until they reach the core. Why is it the only one totally inclined?
Uranus' axis of rotation is sideways concerning the solar system's plane,
with an axis tilt of 97.77°. This produces changes in the seasons in a completely
different way than the other major planets. The rotation of other planets can be
visualized as spinning tops inclined concerning the solar system plane,
while Uranus rotates like a ball rolling inclined. When the solstices of Uranus approach, one pole
continuously faces the Sun while the other is in the opposite direction. Only a narrow band
around the equator experiences a rapid day and night cycle, but with the Sun very low above the
horizon as in Earth's polar regions. On the other side of Uranus' orbit, the poles' orientation
in the Sun's direction is reversed. Each pole receives about 42 years of uninterrupted sunlight,
followed by 42 years of perpetual darkness. Can you imagine that? A planet where the
night lasts 42 years. This situation where the atmosphere doesn't warm for decades can lead to
some interesting atmospheric properties that don't occur on any other planet.
As the equinoxes approach, the Sun aligns with Uranus' equator creating a period of
day-night cycles similar to those seen on most other planets. The most recent
equinox of Uranus was on December 7, 2007, and the next will be in the year 2049.
A consequence of the orientation of the axis is that the polar regions receive more solar energy
during the year than the equatorial regions. However, the temperature of Uranus is higher
at its equator than at its poles. The mechanism that causes this circumstance is still unknown.
The reasons why the axis of the planet is so tilted are not known. However, it is speculated
that perhaps during its formation, the planet may have collided with a large protoplanet capable of
producing this orientation. Another possibility is that the gravitational perturbations exerted
by the other giant planets in the solar system have forced it to tilt this way.
A long and challenging journey As we have appreciated, Uranus
is not a boring planet; on the contrary, it is a fascinating and unique planet,
but there is an excellent reason why, in the entire history of space exploration, only one
mission has visited Uranus: it is challenging. The planet is nearly three billion kilometers
(1.8 billion miles) from the Sun, 20 times farther away than Earth. As a result,
any spacecraft will take up to 15 years to get there, using rapprochement gaps between planets
to take advantage of gravitational assists. Another limiting factor that all spacecraft that
are sent to the far reaches of the solar system have is sunlight. As sunlight is feeble as we
move away from the Sun instead of solar panels, the mission must employ a nuclear power source,
which is more complicated to build and operate, In addition to being much heavier and as we have
already mentioned in past videos, the heavier a ship is, the more expensive it is and what
space agencies least want is to make their projects more expensive than they already are.
Remember that one of the factors that most hinder the execution of space exploration
projects is almost always money; space agencies must justify very well the cost of a mission
so that the government is willing to finance it. Another problem that adds up is communication; in
a video we made earlier about the Voyager probes. "Add at this point an image of the
thumbnail we made over the video of what the earth looks like from Voyagers."
We talked about how difficult it is to communicate with spacecraft that are too far from Earth.
The only way to communicate with a ship that visits the icy giants would be to place a large
satellite dish capable of emitting signals that manage to reach the Earth; as you can imagine,
this would mean, again, increasing the weight and dimensions of the spacecraft.
Not to mention the difficulty of receiving and sending data; at those distances,
the radio signals sent by a spacecraft take more than 20 minutes to reach Earth, and the
communication between the receiver and the sender would consist of 40 minutes, which is a long time.
Therefore, a ship heading to Uranus would have to have programmed a series of tasks
that would have to be executed automatically and without human intervention, something that,
although it sounds simple, it is not if we contemplate that a spaceship moves at more than
20 km / s in interplanetary space, an error of 1 millimeter in the direction and would be the end.
Another significant and little-talked-about obstacle is keeping both engineering and
operations mission teams together for as long as it takes to complete the mission;
this can be up to a decade between launch and the spacecraft's arrival on the planet.
Although it seems insignificant, this problem is why many missions have had to be canceled.
Even others have been delayed years because the team that began working on a mission was not the
same that finished it. Information or codes of great importance are usually lost in the
passage from one team technique to another. This was just what happened with the Voyager
probes, which used VHS-type films to send images, and software made specifically for this task was
responsible for encoding them here on Earth. The equipment that performed that job,
the software, and the people they knew how to use them no longer exist, so today,
it is impossible to retake images with the Voyager cameras, even if they work.
Another example of this problem can be seen in the recent Artemis 1 Mission that aims to take the
next generation of astronauts to the Moon. Many people wondered why the spacecraft and equipment
that were used in the 60s were not simply rebuilt; the reason is that all that information was lost,
the people who knew the codes of the computers, the passwords, those who made the designs,
the mathematical calculations, most of them died long ago. Others replaced the equipment,
In the process, all that information was lost, and therefore it was no longer
possible to rebuild the ships that took humans to the Moon for the first time.
As you can see, even before considering what instruments will be placed aboard a
hypothetical ship that Uranus will visit, you must consider all this.
NASA's new priority It has become clear that
Uranus and Neptune are the least known planets in the solar system. Because of this, NASA has been
trying for years to outline the characteristics of a mission to study these bodies in 2030.
In 2017 a NASA study concluded that it was necessary to study both worlds.
The problem is that there is no money to launch two high-cost probes to the two planets,
so it's time to prioritize. One option is to combine this mission with visiting one
or more Kuiper belt objects. Another is to explore one of the two planets. Until now,
NASA considered both worlds equally fascinating from a scientific point of view,
but in a recent report by OPAG (Outer Planets Assessment Group), the agency has radically
changed its mind. And they think that they should give priority to Neptune.
Why Neptune and not Uranus? Well, because of, or rather, thanks to, Triton,
the largest moon of Neptune. The decision does not cease to be curious because, until recently,
Uranus seemed to have won the battle to be the next protagonist of a space mission.
Uranus and Neptune are equally fascinating. Voyager 2 discovered Neptune was more active
than Uranus. Still, observations from the Hubble Space Telescope and ground-based
instruments have shown that the last planet can be as active or more active than Neptune.
On the other hand, Uranus' moon system is the worst known in the solar system, which compensated
for Triton's presence around Neptune. However, the proximity of Uranus was the main factor in its
favor since it allows flight times sustainable lower than those necessary to reach Neptune.
But OPAG does not support any compromise solution that includes flyby-by probes to the two planets.
The only valid option for them is to send a flagship mission consisting of a 7-ton
orbiter equipped with an atmospheric probe that studies one of the ice giants and its
system of moons in detail. And, since there is no money for two orbiters, you have to choose
Studying the moon system of Uranus or Neptune, on the one hand, the moons of Uranus are the most
unknown; in contrast, we know that Neptune has Triton, a moon in which there is likely water.
Triton has tipped the balance in favor of Neptune because the community of researchers dedicated to
the solar system's ocean worlds has identified it as one of its targets. Neptune's largest
moon probably possesses an internal ocean, a mantle of liquid water comparable to Pluto's.
After all, Triton is a Kuiper belt body captured by Neptune. Ocean worlds include Europa, Ganymede,
Callisto, Enceladus, Titan, etc. They are a priority for NASA because they are the bodies with
the most significant potential for habitability in the solar system. So, according to OPAG,
NASA's next flagship mission after Europa Clipper should be an orbiter to Neptune.
So sadly, and for now, there is no mission to Uranus, at least in the next 20 years. Some
scientists are proposing to NASA to prioritize this planet since the study of exoplanets has
revealed that Uranus closely resembles most planets found so far in other solar systems,
so that it could be the most common type of planet in the galaxy. However, at the moment,
there is still no clear proposal. And you think we will soon see a new
space mission to study Uranus? Do you think we should give
more priority to this planet? Let us know what you think in the comments!