Human exploration of the Earth and our universe is pushing ever-expanding boundaries. Along with renewed exploration of the moon and ongoing exploration of Mars, we have also probed the outer reaches of the solar system, and beyond.
Beginning in 1972, NASA has executed many successful missions to the outer solar system that have exponentially increased our knowledge of Jupiter, Saturn, Uranus, Neptune, Pluto and their myriad of intriguing moons, such as Pioneer 10 and 11, Voyager 1 and 2, Galileo, Cassini, New Horizons and Juno. These missions have also kindled questions that we did not even know to ask a few decades ago. Also, NASA has operated many powerful space telescopes, now including the James Webb Space Telescope, expanding our knowledge of physics and astronomy to the edge of the visible universe and time.
In the 18th century, geologist James Hutton laid the framework for Uniformitarianism, the assumption that the same natural laws and processes that operate in our present-day scientific observations have always operated in the universe in the past and apply everywhere in the universe. This assumption has held true in our observations beyond our planet. It is immensely gratifying to see geologic processes – familiar to us on Earth – shaping our sister planet Mars. Perseverance is this moment exploring an ancient river delta on Mars where flowing water once deposited sediments in familiar progradational deltaic clinoforms. The Huygens probe, brought to Saturn’s moon Titan by the Cassini spacecraft, discovered active meandering rivers and lakes on Titan’s surface. However, the active agent there is liquid methane raining from Titan’s cold nitrogen and methane atmosphere.
In keeping with that assumption of Uniformitarianism, there is a reasonable chance that Mars’ once Earth-like, warmer, wetter geologic past led to the evolution of life. The possibility of life also leads us to the cold, outer solar system.
Europa Clipper Mission
The core of NASA’s Europa Clipper spacecraft has taken center stage in the Spacecraft Assembly Facility at the agency’s Jet Propulsion Laboratory. The craft stands 10 feet high and 5 feet wide. For the next two years, it will be the focus of attention of engineers and technicians in the facility’s ultra-hygienic High Bay 1 as they assemble the spacecraft for its launch to Jupiter’s moon Europa in October 2024.
The Italian astronomer Galileo Galilei discovered the four largest moons of Jupiter – Io, Europa, Ganymede, and Callisto – in 1610, as one of the first humans to turn a telescope to the heavens. He observed the moons orbiting Jupiter and in a flash of insight knew that the Earth must orbit the sun in a similar way.
Anyone can see these four moons of Jupiter in a pair of binoculars, but we did not get detailed views of the Jovian system until Voyager 2 flew by in 1979. The views of Jupiter and its moons were an awe-inspiring revelation. Io revealed many active sulfur-spewing volcanoes. Europa is an ice-mantled, complexly fractured world. Ganymede and Callisto have old, icy surfaces with innumerable impact craters.
The marvels at Jupiter begged for a new mission to orbit and study the Jovian system. The Galileo Mission arrived at Jupiter on Dec. 7, 1995, and studied the huge system until 2003. We now know that Jupiter has a family of 80 moons. Europa is the most intriguing, since it has a 15-kilometer-thick, fractured ice crust that covers a deep ocean of liquid water warmed by tidal flexing. It has twice as much liquid water as the Earth, with organic molecules present. It is likely that Ganymede, Calisto, and Saturn’s moon Titan have comparable amounts of liquid water.
Life evolved in water on Earth and thrives to the deepest depths of our oceans. Billions of years, organic molecules and hydrothermal activity from a rocky core – all of which are suspected to exist on Europa – could have sparked the evolution of life on these icy worlds.
This possibility was the catalyst for the Europa Clipper Mission.
Earth has chemosynthetic organisms feeding off of mineral-rich hydrothermal vents on the ocean floor. Bacteria perform a chemical reaction, chemosynthesis, with carbon dioxide and hydrogen sulphide plus oxygen yielding sugar, sulphur and water. They use the sugar for energy. It is believed that chemosynthesis is also possible in Europa’s oceans.
Europa’s fractured surface ice ridges suggest that fluidized material welled up from the linear fractures (linea). In the fractured chaos regions, which cover a fourth of the Europa’s surface, ice might be only three kilometers thick. Warmer salty water might be upwelling in these regions, thinning the ice, and occasionally welling onto the surface. The linea are colored with organic tholins, so there must be a source of carbon, nitrogen, water and energy to drive organic reactions. Since Europa’s linea features are thought to be significantly thinner than the rest of the ice crust, they could be targets for future landers with nuclear-powered ice drilling capability.
In July 2021, the SpaceX Falcon Heavy rocket was chosen to launch the Europa Clipper spacecraft. The mission will take a 5.5-year trajectory to the Jovian system, with gravity-assist maneuvers around Mars in February 2025, and Earth in December 2026. The Europa Clipper Mission is planned for launch in October 2024 with Jupiter orbit insertion in April 2030. It will study Europa in an elliptical orbit around Jupiter and make 44 close fly-bys of the moon.
The mission is a joint investigation between the Jet Propulsion Laboratory and the John Hopkins Applied Physics Laboratory. The spacecraft will have a science payload of nine instruments contributed by JPL, APL, Southwest Research Institute, University of Colorado Boulder, University of Texas at Austin and Arizona State University.
In addition, the European Space Agency’s Jupiter Icy Moons Explorer launches in 2023, reach Jupiter in 2031. It will fly by Europa and Callisto multiple times before entering orbit around Ganymede.
This Europa Clipper Mission seeks to explore for the three main requirements for life: liquid water, key elements and energy. The goals are to investigate Europa’s habitability while looking for a prime landing site for the future Europa Lander Mission. Specifically, the objectives are to confirm the existence of liquid water within or beneath the ice and study processes of surface ice-ocean exchange. Remote sensing will measure the distribution and chemistry of key compounds and the links to ocean composition. Remote sensing will study Europa’s geology and formation of surface features, including sites of recent or current activity.
The Europa Clipper Mission is equipped with a scientific payload for remote-sensing astrogeology and geophysics as a sophisticated suite of nine instruments to study Europa’s interior and ocean, geology, chemistry, and habitability:
- Europa Thermal Emission Imaging System (E-THEMIS)
- Mapping Imaging Spectrometer for Europa (MISE)
- Europa Imaging System (EIS)
- Europa Ultraviolet Spectrograph (Europa-UVS)
- Radar for Europa Assessment and Sounding: Ocean to Near-surface (REASON)
- Interior Characterization of Europa using Magnetometry (ICEMAG)
- Plasma Instrument for Magnetic Sounding (PIMS)
- Mass Spectrometer for Planetary Exploration (MASPEX)
- Surface Dust Analyzer (SUDA)
“We have a rare and wonderful opportunity with this mission to investigate whether Europa could be an abode for life,” said Curt Niebur, NASA Europa Clipper Program scientist. There are reasonable possibilities for life in the vast ocean of Europa. As astrobiologist Malcolm Walter said (before Jeff Goldblum’s character in “Jurassic Park” used the line), “Life finds a way.” As we find energy and raw materials in the oceans of Europa, we may discover life, indeed, has found a way.
NASA’s proposed Europa Lander Mission concept would be a follow-up mission to the Europa Clipper. The Europa Lander Mission is designed to detect biosignatures on the surface of Europa. The lander will not be capable of drilling through the ice, but Europa’s upwelling subsurface is deposited on the surface, waiting to be sampled.
Titan Dragonfly Mission
The Cassini Mission was the fourth space probe to visit Saturn and the first to enter its orbit exploring Saturn and its moons in unprecedented detail from 2004 to 2017. We now know that Saturn has 83 moons. Titan and Enceladus offer the most promise for organic chemistry that could have evolved extraterrestrial life.
The NASA Dragonfly Mission is planned to send a robotic rotorcraft to the surface of Titan, the largest moon of Saturn. The Dragonfly Mission was chosen in 2019 in NASA’s New Frontiers program, again as a joint investigation between the NASA and the John Hopkins Applied Physics Laboratory. The mission has a planned launch date in June 2027 with Saturn arrival and Titan landing in 2034.
This is a bold follow-on mission to the Cassini-Huygens probe that soft-landed on Titan in 2005. Huygens acquired atmospheric and surface measurements on Titan, detecting tholins, a mix of organic compounds in the atmosphere and on the surface. Titan’s nitrogen and methane atmosphere is 60-percent more dense than Earth’s and filled with hydrocarbon smog. Dragonfly will be the first aircraft on Titan. It will use vertical takeoff and landing capability to traverse between exploration targets. It is designed to study prebiotic chemistry and extraterrestrial habitability. Different geologic settings on Titan will reveal how far prebiotic chemistry has progressed forming key ingredients for life, such as pyrimidines – the building blocks of DNA, and amino acids – the building blocks of proteins.
Dragonfly will be a large quadcopter with double rotors. Each of the rotors will be about 3.3-feet in diameter. Dragonfly will travel at about 22 miles per hour and up to an altitude of 13,000 feet. It will fly up to 30 minutes and traverse up to about 6 miles on a charge. Dragonfly will be powered by a lithium-ion battery charged by a radioisotope thermoelectric generator. It will operate in temperatures averaging 94 Kelvin (−179.2-degrees Celsius). Dragonfly will communicate to Earth with a high-gain antenna.
The Dragonfly rotorcraft has a mass of about 990 pounds (Earth gravity), and will be delivered to Titan inside of a 12-foot diameter heatshield. Surface samples will be acquired with two sample acquisition drills, one on each landing skid. Samples will be analyzed with a mass spectrometer instrument.
The craft will be grounded during the long Titan nights, which last about eight Earth days. Night activities would include sample collection and analysis, and seismological studies like detecting waves on the northern hydrocarbon seas.
The Dragonfly Mission is equipped with a scientific payload for remote sensing astrogeology and geophysics:
- DraMS (Dragonfly Mass Spectrometer) will identify chemical components relevant to biological processes in surface and atmospheric samples.
- DraGNS (Dragonfly Gamma-Ray and Neutron Spectrometer) will study the surface composition under the lander.
- DraGMet (Dragonfly Geophysics and Meteorology Package) is a package of meteorological sensors including a seismometer.
- DragonCam (Dragonfly Camera Suite) is a set of panoramic and microscopic cameras to image Titan’s terrain and scout for scientifically targets.
When Dragonfly arrives at Titan in 2034, the lander will descend to the surface of Titan using an aero-shell and a series of two parachutes. Dragonfly will land initially in dunes at the edge of the dark region called Shangri-La. This region is an immense sand sea of dark, organic material. It will explore this region in a series of flights and acquire samples from selected areas with a diverse geology. Then, it will travel to the Selk impact crater, where there is evidence of past liquid water in addition to tholin organic compounds.
“With the Dragonfly Mission, NASA will once again do what no one else can do,” said former NASA Administrator Jim Bridenstine. “Visiting this mysterious ocean world could revolutionize what we know about life in the universe. This cutting-edge mission would have been unthinkable even just a few years ago, but we’re now ready for Dragonfly’s amazing flight.”
We live in a generation that will witness humans returning to settle and explore the moon, aiming to set foot on Mars to explore for possible past life and pave the way for human settlements, and seeking to discover possible extraterrestrial life in the outer solar system.
