With the end of the Space Race and the retirement of the Space Shuttle, NASA has become stagnant in its efforts to explore space, particularly the Solar System that hosts our home planet Earth. A consistent lack of will, which too often translates into a lack of funding, has relegated the space agency’s exploration efforts into afterthoughts in America’s politics and collective consciousness. This for the country that pioneered the free world’s exploration of space and landed the only humans on the Moon, all while achieving giant leaps in civil rights and toward a more equal society here at home. This stagnation has to stop.
This lack of financial will, however, should not be confused with a lack of vision. With the grand successes of NASA’s Galileo mission to Jupiter and Cassini-Huygens mission to Saturn, the latter of which continues to operate and educate today, two destinations in our Solar System have risen to the top of the science community’s priority targets. These are Jupiter’s icy moon Europa and Saturn’s perpetually-shrouded moon Titan. Scientific missions to each destination have been proposed, and often cancelled, due to the disparity between vision and financial will. All of humanity will benefit from reversing this trend.
Despite its diminutive size, a diameter slightly smaller than the Earth’s Moon, Jupiter’s Europa is suspected to have more surface water than the entire Earth. It is not, however, the highly reflective layer of water ice on the surface that most intrigues scientists. Europa orbits its host planet at a mean distance of 670,900 kilometers (about 420,000 miles). Like its fiery, volcano-ridden sister Io, Europa orbits deep inside Jupiter’s immense gravitational well. This subjects both moons to a process called tidal flexing. The same tidal effects by which the Moon stirs the oceans at high tide on Earth also occur on Io and Europa, only they are magnified exponentially, as Jupiter has a mass of 25,000 Moons. The gas giant thus stretches and compresses its nearest moons with each orbit, constantly churning their interiors.
On Io, this phenomenon manifests through the volcanoes and geysers that constantly spray the moon and its atmosphere with lava, ash, and sulfur plumes, to such an extent that the surface maps of Io date very quickly. By contrast, on the icy Europa, these immense tidal forces fail to melt the surface ice, but instead create heat in the moon’s interior as they manipulate the moon-like giant accordion. Scientists strongly believe that this churning must logically melt some of the ice at some depth, which creates the possibility of an ocean of liquid water spanning the entire moon. This, in turn, raises perhaps the most promising prospect of extraterrestrial life in our Solar System.
Protected by several miles of granite-hard water ice from the blistering bands of radiation Jupiter produces, the environment beneath the ice could potentially host any number of sea creatures, from bacteria to tube worms, even to actual fish. Environments that would seem prohibitive of life have been discovered in abundance here on Earth, particularly among the hydrothermal vents that hug the fault lines of the deep ocean. Yet diverse ecosystems, subsisting on no sunlight and minimal oxygen, have been discovered as well, leading to enthusiastic speculation among the scientific community about what may lie beneath Europa’s ice crust.
NASA’s “holy grail” with regards to exploring Europa would be a lander that includes a pneumatic drill that both heats and penetrates the ice, in the effort to reach the liquid water underneath. With the success of one pioneering mission to penetrate the ice, NASA may even follow up with submersible probes that would swim the depths and search for signs of life. In the meantime, on a scale that would be better suited to present-day technology, NASA and the ESA are drawing up plans for the Europa Jupiter System Mission (EJSM) to launch a pair of orbiters to study Europa and its sister and fellow ice moon, Ganymede. These spacecraft would conduct their work from orbit, possibly paving the way for landers in the future. The Russian Space Agency has even expressed interest in contributing a surface lander to the project, a craft that would launch separately atop a Soyuz-class rocket, and study the surface in situ.
However, NASA withdrew from the consortium in 2012 due to budget cuts. Financial constraints are at the heart of NASA’s stagnant exploration program. By the same token that they jeopardize multiple missions to Europa, budget cuts are likewise threatening to derail another proposed mission to another vital destination, Saturn’s moon Titan.
The second-largest largest natural satellite in the Solar System, smaller only than Jupiter’s Ganymede and larger than the planet Mercury, Titan presents another set of opportunities to study. The only moon in the Solar System known to have an atmosphere, and one thicker than Earth’s, Titan is often regarded as a model for the primordial Earth after it had cooled and before importing its water and carbon from impacting comets. It is also the only moon known to have vast reserves of surface liquid, in the form of ethane and methane lakes. Perhaps of greatest interest, Titan’s thick atmosphere is composed of 95 percent nitrogen, the same gas that makes up two-thirds of Earth’s atmosphere. This isolates oxygen as the main variable that differentiates the two atmospheres. In fact, in a chicken-and-egg phenomenon, Earth became hospitable to life through the introduction of oxygen into the nitrogen-dominated atmosphere, an introduction facilitated by the earliest microbes to live on the primitive Earth and undergo the process of photosynthesis.
What intrigues scientists even further is the simple reality that, about 5 billion years from now, the Sun will swell to become a red giant star, a process that will roast the Solar System’s inner planets, including Earth, while simultaneously raising the temperature on Titan. This change in the moon’s climate should eventually melt the water ice on the surface, which is currently chilled to -190 degrees Celsius and is hard as rock, into liquid water as it exists on Earth. Moreover, the expanding Sun’s output of ultraviolet (UV) radiation will decrease. This process, in turn, will deplete some of the haze in the upper atmosphere of Titan, reducing the “anti-greenhouse” effect that currently reflects much of the already-feeble sunlight Titan receives and presently keeps the moon in a cryogenic freeze.
In conjunction with the European Space Agency, NASA has envisioned a pair of missions to explore this distant snapshot of Earth’s infancy. They will involve a hot-air balloon to probe the atmosphere and a nautical lander to touch down on one of Titan’s methane lakes. The balloon would exploit an atmosphere that is one and one-half times thicker than Earth’s, staying aloft for up to six months and taking measurements of its composition and seasonal changes. The goal would be to study an atmosphere that scientists believe mirrors Earth’s before the biotic introduction of oxygen. It would literally profile Earth’s primordial past while probing Titan’s future as a possible habitat when the swelling Sun has evicted humanity from Earth.
The lake lander, called the Titan Mare Explorer (or TiME), would touch down on one of the many lakes that exist in the moon’s northern hemisphere. The lander would be powered by a small nuclear battery that would keep it operating for approximately 3 to 6 months. It would deploy a mast that might draw a resemblance to a sailboat, but the mast would contain nothing more than a camera. Its mission would be similar to the balloon’s. It would measure and help scientists understand the conditions on Titan, which has come to be called a “pre-biotic laboratory,” a confluence of chemistry and climate that would appear ripe for life to take hold and introduce the missing link of oxygen.
None of these missions, however, can proceed without adequate funding. This is a reality that has been crippling NASA’s space exploration efforts in the last couple of decades. These proposed expeditions stand to provide invaluable insight into the origins and future of Planet Earth, and may even help answer the ultimate question in astronomy, whether Earth hosts the only living organisms in the Universe. In Europa especially, and in Titan to a lesser degree, humanity has opportunities right in our own Solar System to explore whether we truly are alone.
Konstantin Tsiolkovsky, the Russian rocketry pioneer who as early as the 1890s envisioned and piloted multi-stage rockets with pressurized, closed-environment capsules taking humans into the heavens, famously wrote “The Earth is humanity’s cradle, but mankind cannot stay in the cradle forever.” It is inevitable that in a couple of billion years, should our species survive that long, we will have to leave Earth for another celestial home. Titan may very well prove to be such a destination, as the swelling Sun warms its atmosphere and strips away its most photo-reflective layers of haze. With so many unknowns, and untold numbers of secrets that lie beneath Europa’s ice crust and Titan’s hydrocarbon haze, an incredible amount of new exploration is needed. We literally have yet to scratch the surfaces of these two moons, and the time is ripe to do so.
By Emanuel Ardeleanu
Lopes, Rosaly, et al. “Io: The Volcanic Moon.” Encyclopedia of the Solar System. Academic Press. pp. 419–431. ISBN 978-0-12-088589-3. (Print)