The European Space Agency (ESA) heads for Jupiter in 2023! The spacecraft will launch from South America and arrive at Jupiter in 2031. After orbit insertion at Jupiter, the spacecraft will spend three years observing both Jupiter and three of its largest moons.  

The mission is the first “large class” mission in the ESA’s Cosmic Vision 2015-2025 program. JUICE (JUpiter ICy moons Explorer) is the ESA’s project. The spacecraft will spend seven or eight years traveling toward Jupiter with a tentative arrival date/Jupiter orbit date of 2031.

The mission will conclude when the spacecraft intentionally crashes into one of Jupiter’s moons.

Flight Paths

The flight path from Earth to Jupiter will last approximately seven to eight years. The spacecraft will orbit Jupiter’s moons for about three and a half years collecting data. 

Flight Path to Jupiter

The JUICE mission will launch from the European Spaceport in Kourou, French Guiana. The Ariane 5, “The Heavy Launcher,” will carry the spacecraft.  

The spacecraft will take advantage of gravity assists from Earth (three different times!), Venus and Mars to increase the spacecraft velocity and reduce the flight time.

Flight Path around Jupiter’s Moons

JUICE will use the gravity from Ganymede, Callisto, and Europa to adjust its flight trajectory during flybys past each moon to stabilize and optimize its orbit. JUICE will collect data from Jupiter, Callisto, and Europa during the flybys.  

JUICE will be placed into a highly elliptical orbit around Ganymede before the mission’s conclusion. 

Timeline

In 2022, the ESA finalized the launch window for the JUICE mission. Launching the spacecraft within this time window will allow gravity assistance from the Earth and Venus.

Date	Event
April 5th-25th 2023	Launch
August 2024	Earth flyby-Gravitational Assist (1)
August 2025	Venus flyby
September 2026	Earth flyby-Gravitational Assist (2)
January 2029	Earth flyby-Gravitational Assist (3)
July 2031	Enter Jupiter Orbit
July 2032	Europa flybys
August 2032-August 2033	Callisto flybys
December 2034	Enter Ganymede orbit
+200 DAYS	Possible mission extension
September 2035	Crash spacecraft into Ganymede

Mission Objective

JUICE has different objectives for three of Jupiter’s moons, Ganymede, Callisto, and Europa.

Ganymede

1. Ocean water (sub-surface) characterization
2. Search for theoretical subsurface water reservoirs 
3. Mapping the surface of the moon
   1. Topographical
   2. Geological
   3. Compositional
4. Moons core characterization
   1. Internal mass distribution
   2. Evolution and dynamics.
5. Exosphere 
6. Magnetic fields

Callisto 

Ganymede and Callisto have the same objectives. 

Europa

1. Organic molecules
2. Formation of surface crust
3. Non-water-ice elemental composition

What are Scientists the Most Excited About?

In a word, Habitability. Planetary scientists spent decades looking for planets in our galaxy similar to Earth in relation to their atmosphere and elemental composition.  

Today scientists have shifted their telescope lens (so to speak) and are instead looking at planets and moons that might have subsurface oceans that can support life. 

The Galilean moons of Jupiter are more similar to other planets than they are to other moons. Long considered dormant, cold, icy blocks of ice, the Galilean moons have planetary scientists enthused about potentially habitable underground oceans. There are two vital primary questions planetary scientists hope to be able to answer based on the data from JUICE.

1. Does extra-terrestrial life exist? (Hint: Think single-cell organisms, not sharks and whales.)
2. How are planets formed?

It’s Getting Busy Around Jupiter’s Moons!

The European Space Agency, NASA, and China are planning large-scale missions to Jupiter and its moons in the coming years. 

• The ESA will launch the JUICE mission in 2022.
• NASA plans to send the Europa Clipper toward Jupiter’s moon Europa in 2024. The spacecraft should arrive around the same time window as the ESA’s JUICE. The Clipper will collect data to allow scientists to understand its capability of supporting life.  
• China announced they’ll send the Tianwwen 4 to Jupiter’s moon Callisto in 2030. According to the China National Space Administration, “The scientific goals are still under consideration.”

Launch Time!

The eyes of the world will be on the JUICE mission when it arrives at Jupiter’s moons. With an eight-year flight time and a three to four-year mission after arriving at Jupiter, JUICE will send data for scientists to evaluate and debate for a long time. We can’t wait! 

The Europa Clipper Mission is scheduled to launch on October 10th, 2024.  Europa is one of the most favorable locations in the solar system to find a habitable environment. 

The Europa Clipper is tasked with collecting the data to allow scientists to determine if there are locations below Europa’s icy crust capable of supporting life. It is the first mission to explore an Ocean World. 

Mission Overview

The Europa Clipper is one of NASA’s flagship planetary science missions.  With a projected budget of five billion dollars, expectations are high. While expectations are high, the mission objective isn’t to find life.  The mission objective is to determine if there are locations beneath the surface of the moon that could support life. 

A different mission, based on the results of the Europa Clipper mission, would naturally move toward surface exploration.    

The Europa Clipper will orbit Jupiter for four years.  During that period, the spacecraft with perform over fifty Europa flybys.  The Clipper will map more than 80% of Europa’s surface with a maximum camera resolution of three feet (one meter) per pixel. 

Scientific Objectives

The Europa Clipper has three primary science objectives:

1. Determine the thickness of the Moons shell and its interaction with the surface
   1. Is there liquid in the shell? 
   2. Is there liquid beneath the shell?
   3. What’s the size and salinity of the ocean?
   4. Do objects (organic or inorganic) rise up to the top of the water from the depths of the ocean?  Do objects drop to the ocean floor from the bottom side of the crust?
2. What is the composition of the ocean?
   1. Does the ocean have the key ingredients to allow living organisms?  
   2. Sustain living organisms?
3. How did the moon’s surface features form?
   1. How did Europa’s surface features form?
   2. Has there been any recent activity on the surface?  (Plumes or crust plates.)

Spacecraft Dimensions

The Europa Clipper is one of the largest spacecraft that NASA has ever built when the solar arrays are extended.  

• Spacecraft Main body:
  • 16 feet (5 meters) tall
  • 100 feet wide (30.5 meters) wide when the solar arrays are fully extended.

Scientific Components

The Clipper contains nine scientific instruments with overlapping capabilities.  Due to the high radiation levels from Jupiter, the instruments will be housed in an aluminum-titanium vault. 

1. Imaging System (EIS).  Wide and Narrow-angle imaging. 5X higher resolution than previous images. 
2. Thermal Emission Imaging (E-Themis).  Analyze infrared light to determine surface temperature. Looking for variants that indicate recent activity. 
3. Ultra Violet Spectrograph (EUVS). Analysis of UV data to determine
   1. Is there actually a water ocean? 
   2. Surface and plume elemental composition
4. Spectrometer (MISE).Infrared light analysis. Organics, salts, compounds, sulfates.  Paints a picture of the moon’s geologic history.
5. Magnetometer (ECM).  Magnetic strength and orientation measurement.  Will determine ocean depth and salinity. 
6. Gravity/Radio science Measure how the moon flexes under differing Jupiter gravities to indicate Europa’s internal composition. 
7. Radar– (REASON) ice penetrating to measure the thickness of the icy shell and search for water below the shell.
8. Mass Spectrometer (MASPEX). Gas identification from the surface, atmosphere, and ocean.
9. Surface Dust Analyzer (SDA). The speed and trajectories of particles entering the analyzer identify the particle’s area of origin on the moon. Individual molecules are ionized, and their mass and composition are identified. 

What Happens After the Mission?

The next step following the Europa Clipper mission greatly depends on what the mission finds between 2030 and 2034 during the moon flybys  If the mission finds that Europa does in fact have an ocean and that the conditions are favorable for life, a new mission that includes a lander must be discussed. 

A return trip to Europa to investigate life within the ocean would require both a rover and a submersible device.  A method would need to be crafted, evaluated, and perfected to collect analysis specimens.  

How would analysis be performed in a high-radiation environment?  These are all questions for a later date. We first need to collect data from Europa and see what mysteries she’s willing to share with us. 

Mercury is our solar system’s smallest planet. It’s only slightly larger than Earth’s moon. And like the moon, it has almost no atmosphere. As a result, craters from debris impact litter Mercury’s surface.

Mercury and its neighbor Venus are the only planets in our solar system without any moons. So let’s dive right and learn some fun facts about Mercury, the first planet from the Sun.

Why Doesn’t Mercury Burn Up Since It’s So Close To The Sun?

Since Mercury is sun-scorched, why doesn’t the planet burn up? Mercury’s dayside superheats to around 800 degrees Fahrenheit (430°C). But at night, it plummets hundreds of degrees below freezing, down to -290°F (-180°C). It’s so cold that ice may form in some surface craters.

While the Sun superheats one side of Mercury, it’s not hot enough to melt the dense planet. The radius of its metallic inner core is 1,289 miles (2,074 kilometers). That’s almost 85% of the planet’s entire radius.

Evidence exists that part of the inner core is molten or liquid. It is similar to the Earth’s solid inner core, surrounded by a fluid, molten iron, and nickel outer core. Mercury’s outer shell is similar to Earth’s rocky mantle and crust.

What Spacecraft Made Visits To Mercury?

While humans haven’t traveled to the planet, Mercury exploration is still critical. Past and ongoing investigations seek to answer some of our most pressing Mercury questions.

Mariner 10

Mariner 10 was the first spacecraft to make flybys of Mercury, collecting data as it passed.

• Three flybys in 1974 and 1975
• The spacecraft took more than 2300 images.

MESSENGER

The first spacecraft to orbit Mercury was the MESSENGER.

• MErcury Surface, Space ENvironment, GEochemistry, and Ranging mission
• Launched from Cape Canaveral, Florida, on August 3, 2004.
• January 14, 2008, orbited at a distance of 125 miles.
• October 6, 2008, orbited at a distance of 124 miles.
• September 29, 2009, orbited at a distance of 124 miles.

BepiColombo

The European Space Agency’s BepiColombo completed two flybys of Mercury with plans for more.

• Flyby dates: Oct 1, 2021; June 23, 2022; June 20, 2023; Sept 5, 2024; Dec 2, 2024; Jan 9, 2025
• Arrival at Mercury: December 5, 2025
• Beginning of routine science operations at Mercury: Expected in February 2026
• Mercury exploration answers sought:
  • Where did it form?
  • Is there water on Mercury?
  • Is the planet dead or alive?
  • Why is Mercury so dark?
  • Why does Mercury have a magnetic field?

How Long Would Humans Survive On Mercury?

Because of its temperature extremes and the planet’s solar radiation, it’s unlikely that life as we know it could exist on Mercury. Humans could not survive at all. 

Venus is warmer

Although Mercury is closer to the Sun, it is cooler than Venus. Venus has a denser atmosphere and higher albedo, the highest in the solar system at 0.90. So that means it reflects more of the Sun’s heat than it absorbs. But once the heat gets reflected, it struggles to pass through Venus’ thick atmosphere. So heat gets trapped.

Mercury is colder

In terms of temperature, Mercury is the opposite of Venus. Mercury’s thin atmosphere and low albedo allow it to release or absorb most of the heat it receives. Mercury receives four times more of the Sun’s energy and absorbs almost nine times more than Venus. But it’s still cooler than its neighboring planet.

Rotation around the Sun

Mercury rotates very slowly. One complete rotation takes 59 Earth days. Mercury travels around the Sun more quickly than any other planet, taking only 88 days to travel around the Sun. Because of this slow spin and fast rotation around the Sun, Mercury only has one sunrise every 180 days. 

Standing stationary on the planet, you’ll be in the dark for six months out of every twelve Earth months.

Summary

Although Mercury is inhabitable to life as we know it, scientists are still gathering data about the planet. Planetary scientists hope that BepiColombo will provide answers about how Mercury was formed, its magnetic field, and its core.

The Uranus Orbiter and Probe is scheduled to launch in 2031/2032. A gravity assist from Jupiter will slingshot the Orbiter and Probe toward a 2044/2045 Uranus arrival. 

The Uranus Orbiter and Probe mission may bog down here on Earth due to budgetary issues or competing NASA missions before the launch date. If the 2031 or 2032 launch date is missed, it will not be possible to obtain a gravity assit from Jupiter. 

Lacking a gravity assist, the Uranus Orbiter and Probe will arrive at Uranus in 2053.

Why Visit Uranus?

Funding competition is fierce between space exploration projects to determine which projects will move forward. Some projects proceed after a preliminary feasibility study. 

Planetary Scientists would like to explore both ice giants Uranus and Neptune. Budgets, timelines, and politics come into play.  

1. Finance
   1. Spacecraft flight time to Uranus with a gravity assist is roughly a decade.  
   2. Flight time to Neptune is approximately twelve years. 
   3. Time is money. Estimates add $200 million to the baseline project if Neptune is selected instead of Uranus. 
   4. Spacecraft requires a larger rocket to reach Neptune. 
2. No significant exploration
   1. There have been zero dedicated missions to Uranus.  
   2. Most of our knowledge of Uranus is from the Voyager 2 mission.  
   3. Voyager 2 flew by Uranus in January 1986 on its way out of the solar system. 
3. Similarities to other exoplanets
   1. Astronomers have found over five thousand exoplanets in other star systems that appear very similar to our “ice-giants.”  
   2. Lacking exploration and a baseline understanding of our solar systems’ ice-giant planets makes comparison impossible. 

The National Academies of Sciences, Engineering, and Medicine voted in 2022 that NASA’s primary planetary science project for the next decade should be a mission to Uranus. The Uranus project is the number one priority flagship mission, and that’s a big deal.

NASA Mission Classification

NASA has three types of mission classification. The Discovery, New Frontiers, and Solar System Exploration/Flagship missions. The program classification is for small, medium, and large space exploration projects.

Discovery Program

• Addresses vital scientific questions about the solar system
• 450 million dollar budget cap, excluding specific hardware/software/analysis and project partner contributions
• New launch every thirty-six months
  • Goddard’s DAVINCI+ will launch in 2029 to explore Venus 

New Frontiers Program

• Addresses high-priority goals that the planetary science community has established
• 850 million dollar budget cap, excluding particular hardware/software/analysis and project partner contributions
• New launch every sixty months
  • Dragonfly will launch in 2026 to explore Saturn’s moon, Titan

Solar System Exploration Program/Flagship Missions

• High-priority, “large” missions based on the planetary science community input
• Big budget. Previous missions have cost billions of dollars.
• NASA leads the project
  • Mars Exploration Program  

Uranus Mission Objectives

The spacecraft arriving at Uranus will have two components. An Orbitor that will collect data as it circles Uranus. The Orbitor will release a Probe into Uranus’ atmosphere.

1. Orbitor-Will orbit around Uranus. Data collection from Uranus and its moons.
   1. Magnetic fields
   2. Why is the planet so cold?
   3. Rotation. Uranus has an axis rotation of approximately 98 degrees. (Earth is about 23 degrees.) How/Why did this happen?
   4. Ring composition. Uranus has 13 rings, but little is known about them. We know that they’re red, blue and grey. What’s the elemental composition? How were the rings formed?  
   5. Moons-
      1. Do the largest moons have oceans under their icy crusts?
      2. What is their regolith composition?
2. Probe-Will be deployed through the Uranus atmosphere to determine
   1. Atmosphere composition
   2. Atmospheric winds source?
   3. Wind speed as a function of depth
   4. Thermal stratification 

Uranus Orbiter and Probe-Technical development

The National Academies of Sciences, Engineering, and Medicine selected the Uranus mission based on NASA’s preexisting space exploration capabilities and the technology available today. No new technology needs development for inclusion in the Uranus Orbitor and Probe. It’s a “shovel-ready” mission.  

Mission planning, spacecraft manufacturing, and concrete mission objects must be defined to begin planning for a specific launch date.  

Wrap up!

A project that requires several decades of active engagement, both operationally and financially, will require Herculean efforts to reach fruition. NASA must soon decide if they’re up to the task.  

The Voyager spacecraft were launched in 1977. Today, 46 years later, both spacecraft continue to transmit data back to Earth. NASA hoped the spacecraft would remain functional for five years!    

The primary mission of the spacecraft was the exploration of Jupiter, Saturn, their rings, and their moons.  Once the primary missions were complete, Voyager 2’s trajectory was modified to send it past Uranus and Neptune. 

To date, Voyager 2  is the only exploration to have collected data from the ice-giants Neptune and Uranus. Today both Voyagers are traveling toward far-flung constellations. 

Mission Milestones

Two Voyager spacecraft were launched in 1977.  The first spacecraft launched was named Voyager 2. The second spacecraft launched was Voyager 1.  Voyager 1 was given the “1” after its name because it would reach Jupiter and Saturn before Voyager 2.  

Event	Voyager 1	Voyager 2
Spacecraft Launch	Sept. 5, 1977	Aug. 20, 1977
Jupiter flyby	Mar. 5, 1979	Jul. 9, 1979
Saturn flyby	Nov. 12, 1980	August 26, 1981
Uranus flyby		Jan. 24, 1986
Neptune flyby		Aug. 25, 1989
Interstellar Space Entered	Aug. 1, 2012	Dec. 10, 2018
Fired trajectory correction thrusters		July 8, 2019

Where are they today?

Today both Voyagers are a long, long distance away from Earth.  Even though Voyager 2 launched before Voyager 1, Voyager 1 is traveling faster.  

	Voyager 1	Voyager 2
Approximate distance from Earth (Miles)	14.8 billion	12.2 billion
Speed (mph)	38,026	34,390
Communication Lag (hh:mm:ss)	22:05:28	18:25:45

Fun fact: Each year, between late February and early June the Earth is moving towards the Voyagers faster than the Voyagers are traveling away from Earth.  The distance from Earth to the Voyagers decreases!  As the Earth travels (in orbit around the Sun) further away from the Voyagers, the distance increases.  When space agencies discussion planetary exploration “launch windows”, this is what they’re discussing.

Why is Voyager 1 further away from Earth than Voyager 2?

The speed of Voyager 2 decreased after its flyby with Nepture and its moon Triton.  

• The optimal trajectory would maximize the effect of a planetary slingshot and increase the spacecraft’s speed.  
• A second trajectory was utilized to maximize Voyager 2’s ability to collect data from a closer flyby of Triton.  (Does it matter if Voyager 2 reaches a “destination” in 42,000 years versus 40,000 years?)  

Where are they going?

Now that they’ve completed their missions within our solar system, where are the Voyagers going?

Voyager 1

Headed toward the constellation Ophiuchus.  The estimated arrival date is the year 38,249 AD.  Voyager 1 will pass 1.7 light years from Gliese 445.  NASA didn’t have a specific plan on where to send Voyager 1 after it completed its Saturn and Titan flybys.  Gliese 445 was more or less straight ahead, so that’s the direction Voyager 1 is heading.

Voyager 2

Headed toward the constellations of Pavo and Sagitarrius.  The estimated arrival date is in the year 42,023 AD.  Voyager will pass roughly 1.7 light years away from Ross 248. 

Voyager discoveries

• Jupiter
  • Interacting hurricane-like storms
  • Erupting volcanos on Lo
  • Hints of an ocean beneath Europa
  • One new moon
• Saturn
  • Small moons in the F-Ring
  • Titan has a dense nitrogen atmosphere 
  • Methane clouds and rain
• Uranus
  • Ten new moons
  • Five new rings
  • Two new rings
  • An ocean of boiling water roughly 500  miles below the cloud tops
• Neptune
  • Five new moons
  • Four new rings
  • Great dark spot
  • 1,000 Mile Per Hour winds
  • Trition has erupting geysers
• Interstellar
  • The heliosphere, the location where interstellar space starts and the suns solar winds stop, isn’t the shape that astronomers expected to be.  
  • Cosmic rays are 3X stronger outside the heliosphere than inside it
  • Small amounts of gas detected in interstellar space.

Wrap up

The Voyagers will soon fall silent and cease broadcasting data as their power supplies are expended.  Yet, Voyager’s mission to address the fundamental questions of science remains unanswered.  What is the universe made of? Where did life begin? Are we alone in the universe?  

Perhaps 40,000 years from now, one of the Voyager spacecraft will invoke questions about Earth from a civilization far away from Earth’s shores. 

99.5% of all the mass orbiting around Neptune is part of the moon, Titan.  Neptune’s largest moon, Triton, was discovered on October 10, 1846. English astronomer William Lassell found it just 17 days after the discovery of Neptune itself. Triton is the seventh-largest moon in the solar system and the only large moon with a retrograde orbit. 

Triton’s Characteristics

With a composition similar to Pluto and its retrograde orbit, scientists think Triton was a dwarf planet from the Kuiper Belt.

The Moon’s Size

Triton is a rocky, icy world with a diameter of about 1,700 miles (2,700 kilometers.) To put that in perspective, it’s about 4.7 times smaller than Earth but nearly the size of our moon. Triton is also larger than the dwarf planet Pluto.

Because of its large size, astronomers believe Neptune’s other moons probably formed after Triton’s capture. Moreover, they believe the capture event would have significantly disrupted or destroyed any satellite system around the planet. So the moons we see today are smaller and likely newer than Triton.

The Moon’s Makeup

Triton is full of volcanic activity caused by the Sun’s heat. 

• A thin atmosphere of icy nitrogen and methane 
• Rock and metal core. 
• The surface consists of smooth volcanic plains. 
• Mountains and craters are formed by frozen lava flows.

The moon’s density is twice that of water, higher than most other outer planet moons. The higher density likely signals a very rocky core.

The Moon’s Orbit

Triton’s retrograde orbit means it travels in the opposite direction to the planet’s rotation. This orbit direction is likely due to Triton being a captured object rather than a moon formed with Neptune.

Another orbital fact is that, like Earth’s moon, Triton and Neptune share a synchronous rotation. So one side of Triton’s face is constantly exposed to Neptune. 

But unlike our moon, Triton’s orbital inclination means its poles alternate turns facing the Sun. Since Neptune takes 165 Earth years to travel around the sun, each of Triton’s polar regions spends about 80 years soaking up the solar heat.

Is There Life on Triton?

Does Neptune’s moon, Triton, bear consideration as humans continually seek the possibility of life in outer space? Probably not.

The moon has mild winds, similar to our moon. But due to the thin atmosphere, you probably wouldn’t feel them. However, when Voyager 2 flew over Triton in 1989, it measured the moon’s temperature at -391 degrees Fahrenheit (-235 degrees Celsius.) So the surface is too cold for life as we know it to exist. 

The spacecraft measured the moon’s atmospheric pressure at 20,000 times less than Earth’s surface pressure. And finally, Triton has shallow gravity, about eight times lower than ours.  

If life on Triton were possible, it wouldn’t be like life on Earth. For example, even if you lived on Triton’s “sunny pole” for its eighty-year stretch, you would still receive no benefit from the sun’s warmth. 

On the other hand, if you lived in an area of Triton that does experience night and day, the Sun would only be a tiny blip on your horizon. And because of Triton’s retrograde orbit, you would see the faraway Sunrise in the west and set in the east, opposite to what we see on Earth.

How The Moon Got Its Name

This moon’s name comes from the Greek demi-god and merman, Triton. Half man and half fish, he was the son of Amphitrite and Poseidon (Neptune.) Since all Neptune’s moons have names from the Greek water gods and nymphs, Triton fits.

Additionally, Triton was known simply as “the satellite of Neptune” until Neptune’s second moon, Nereid’s discovery in 1949. 

Conclusion

Triton is Neptune’s first discovered and largest moon. Its freezing temperatures make it uninhabitable to life as we know it, even though its surface shows smooth areas. This icy moon likely began as a dwarf planet before Neptune forced it into her orbit.