The Nautilus Mission

The bottom of the ocean is one of the most unknown places on Earth. Deep canyons and high seamounts dominate the landscape. There are black smokers, small vents in Earth's crust, spewing hot water and toxic chemicals into the water. There is no plant life; sunlight cannot penetrate water that deep. The animals that live down there come in odd, pliable shapes, and some use their own bioluminescence to lure prey in. Even though it is on the same planet, the deep ocean is not of this world.

The Papahānaumokuākea Marine National Monument.
From: https://www.papahanaumokuakea.gov/

It is because it is so unknown that marine scientists are so eager to explore it, and one current mission is doing just that. The Nautilus Expedition is a massive effort to characterize and study the geology, biology, and archaeology of a few key areas of the Pacific Ocean between Hawaii, California, and Alaska. Currently, the ship is west of Hawaii, in the Papahānaumokuākea Marine National Monument (MNM), the largest marine conservation area in the world. The mission is operated by the Ocean Exploration Trust, a non-profit organization founded in 2008 to engage in pure ocean exploration. Its founder, Dr. Robert Ballard, is the man is credited with discovering the remains of the ill-fated Titanic, and is current a National Geographic Explorer in Residence. If something is going to be discovered, this is the team to do it.

So what are they looking for? For one, they are now looking closely at the underwater geology around tectonic plate boundaries, and the western coast of North America is an excellent place to do it. Multiple tectonic boundaries, including the Cascandia fault line of the subducting Juan de Fuca plate, are responsible for creating the landscape of the west coast. The Nautilus is there to photograph and map areas of the seafloor that have been missed by previous studies, and to measure the chemicals in the ecosystem around it.

Dr. Marc Fries examines this fragment of fusion crust that
may have come from a meteorite that fell in March 2018.
Picture by Susan Poulton, Ocean Exploration Trust.

Its trek began in Southern California, where it studied the deposits of underwater landslides caused by movement along the San Andreas fault, and traveled up to the Cascadia Margin near Washington and Oregon. As it moved from Astoria, WA to Sydney, British Columbia (Canada), the Nautilus also looked for fragments of a meteorite that fell in March 2018. Preliminary findings indicate that they did indeed collect two small pieces of the fusion crust that forms on meteorites as they burn up in Earth's atmosphere, and it's all because of the Nautilus mission.

The Cascadia Margin is not just of geologic interest; the large volumes of methane gas and hydrate stored in the area makes it an interesting spot for studying the chemistry of the area as well. According to the Nautilus website, "establishing a baseline by documenting and characterizing these sites is timely because geological events, such as earthquakes or submarine landslides, could result in important environmental impacts due to sudden methane release." Over the past two years of research, the Nautilus team has discovered over 2700 bubble streams at 1000 distinct locations along the Cascadia Margin. Before this mission began, it was unclear exactly how much methane was near the Cascadia fault, and how (or even if) it was being released.

As impressive as the geology and chemistry are, perhaps the most awe-inspiring is the biology discovered. At almost every location, the Nautilus stayed for at least two weeks, taking pictures and streaming live video narrated by the crew and scientists on the expedition. One of the best parts of exploring is being surprised by what is found, and this video is an excellent example of this. Taken by the Nautilus crew on September 20, 2018, this video is rare footage of an animal called the pelican (gulper) eel in Papahānaumokuākea MNM. And this was only one of the animals observed!

As it traveled to Hawaii, the Nautilus also studied multiple geologic features called seamounts, which are undersea volcanoes that have not breached the ocean's surface yet. Before the Hawaiian islands were, well, islands, they began as seamounts. Over a long period of time, the underwater volcanic eruptions built up the seamounts until they became a large island. These eruptions still happen, but because of the "hot spot" volcanic activity near Hawaii, the volcano's position is not constant. A new seamount, and future Hawaiian island, is being formed right now off the southeast coast of the large island of Hawaii. Its name is Lō'ihi, and its exploration has the potential to tell us about the habitability of other places in our solar system. From the website:

"The expedition of Lō'ihi marks the beginning of the multi-year SUBSEA (Systematic Underwater Biogeochemical Science and Exploration Analog) Research Program, a partnership between NASA, NOAA, and various academic centers. Bringing together both ocean and space exploration teams aboard E/V Nautilus, SUBSEA blends ocean exploration with ocean worlds research to address knowledge gaps related to the habitability potential of other planets in our Solar System." 

A "gripper" used for collecting samples from seamounts. This novel
tool was developed by the Jet Propulsion Laboratory, and is mounted
on the ROV Hercules, one of the robots on the Nautilus expedition.

 While it was around Lō'ihi, it documented the biological communities that live around the seamounts it observed. Because Lō'ihi is an isolated seamount (one that is not near any tectonic plate boundary), it is considered a strong analog for any kind of venting system that might exist on an ocean world like Europa, an icy moon of Jupiter. By collecting samples from fluid venting locations, geologists and biologists will be able to study the interaction between a seamount and the life that survives there. How cool is it that studying the environment around seamounts in the Pacific can tell us about potential life on other planets? 

It is impossible to put the full scope and findings of the Nautilus mission into a simple blog post, but these are just a few of the highlights that happened in the past few months. If you'd like to read more or follow along with their live-streaming, the website is here: http://www.nautiluslive.org/

Happy exploring!

The History of the Spherical Earth Idea

When I was in elementary school, I learned that the Earth was round. I even remember a silly rhyme in a cartoon I watched in school about Christopher Columbus, who "proved" the Earth was round. To me, the fact that the Earth is round seems almost like an instinct. That being said, I never looked up the history of why and how it's known the Earth is round. Today I started to correct that.

The idea that the Earth is a sphere can be traced back as far as the ancient Greeks. Although the idea is attributed to Pythagoras, a Greek polymath most famous for his Pythagorean theorem of triangles, both he and his contemporary Parmenides of Elea are known to have taught the idea of a spherical Earth. Moreover, it is possible the discovery was made by another Greek and falsely associated with Pythagoras by historians. Aristarchus and Eratosthenes improved on this work by estimating the circumference of the Earth, and noting how the visible constellations changed as the observer traveled nearer to and farther from the equator.

It is also possible that other cultures (Chinese dynastic empires, African tribes, Egypt, and Native Peoples in the Americas) noted evidence that the Earth was round, but few, if any, records of these people survive. Future discoveries may change this. In ancient India, for example, a Greek ethnographer wrote in 300 B.C.E. that the Brahmans (the high scholarly caste in Hindu society) believed that the spherical Earth was the center of the universe. As Hellenistic ideas spread via Alexander the Great's conquest, the Greek ideas merged with those of the Brahmans, and survived well into the next millennium. Aryabhatta I, an classic Indian astronomer and mathematician who lived from 476–550 C.E., wrote in his work, the Aryabhattiya, that the Earth was spherical. He also made an incredibly accurate estimation of the Earth's circumference of 4,967 yojanas, which is equivalent to 24,835 miles. The equatorial value of Earth's circumference is today calculated at 24,901 miles.

In any case, the spherical Earth idea was a moderately popular one in the ancient world, as it persisted throughout Greek dominance and was later adopted by Roman astronomers as the standard. Later on, Ptolemy of Alexandria wrote one of his best-known books, Almagest, in which he defended and built on the arguments for a spherical Earth. He also argued that the Earth could curve in both north/south and east/west directions. The Almagest remained one of the standard astronomy texts for the next 1,400 years. As Europe experienced its Medieval period, the knowledge of a spherical Earth was retained by monks translating ancient Greek and Roman texts. It was also kept alive, and eventually reintroduced to Europe, by many Muslim astronomers, including Ibn Hazm, Al-farghānī (Alfraganus), and Abu Rayhan Biruni. These and other early scholars used this information to develop spherical geometry, an important tool still very much in use today.

A page from Almagest. U.S. Library of Congress.

So exactly how did they all know that the Earth is spherical? Much of it came from the knowledge of sailors. For example, as mountains appeared over the horizon from the top down. Had the Earth been flat, the mountains should have appeared in full as soon as the ship passed any obstructing object in front of it. Another piece of evidence is the shape of the terminator on the moon. A solar terminator is the line that divides the "day" from the "night" side of a planetary body. For us here on Earth, it's the line edge of the shadow that passes over the Moon when it's not full. Ancient astronomers recognized this line as a representation of the shape of the Earth as it passed between the Moon and the Sun. This line is curved, and so the shape of the Earth must too be curved.

https://www.farmersalmanac.com/terminator-22380

Finally, there was the sky itself. The sun is always directly above one point on Earth at solar noon, and this happens predictably for a single location on a yearly schedule. The north star, Polaris, never moves from its place in the night sky, but its declination, or height above the horizon, does change with an observer's latitude on Earth. There are also stars that are not visible from certain points on Earth. If the Earth were flat, then all stars should be visible at all times, as a view from a plane should only rotate in one direction. This logic, coupled with knowledge of geometry, was yet more evidence for a spherical Earth.

Of course, the fact that Ferdinand Magellan and his company sailed completely around the globe between 1519 and 1522 was perhaps the most solid piece of evidence for a spherical Earth before the space age. Now, satellites have orbited the Earth, Moon, Mars, Mercury, Jupiter, and Saturn, returning pictures of all of these that show they are spherical. It would not be possible to orbit a flat plane. Why planets are spherical is another discussion. For now, it is enough to discuss an abridged history of the spherical Earth idea and a few of many pieces of evidence that support it.

Sources:
Burkert, Walter (1 June 1972), Lore and Science in Ancient Pythagoreanism, Cambridge, Massachusetts: Harvard University Press, ISBN 0-674-53918-4, page 306.
https://en.wikipedia.org/wiki/Spherical_Earth
https://www.scientificamerican.com/article/why-are-planets-round/
https://www.livescience.com/60544-ways-to-prove-earth-is-round.html
Direct adoption by India: D. Pingree: "History of Mathematical Astronomy in India", Dictionary of Scientific Biography, Vol. 15 (1978), pp. 533–633 (554f.); Glick, Thomas F., Livesey, Steven John, Wallis, Faith (eds.): "Medieval Science, Technology, and Medicine: An Encyclopedia", Routledge, New York 2005, ISBN 0-415-96930-1, p. 463
Cormack, Lesley B. (2015), "That before Columbus, geographers and other educated people thought the Earth was flat", in Numbers, Ronald L.; Kampourakis, Kostas, Newton's Apple and Other Myths about Science, Harvard University Press, pp. 16–22, ISBN 9780674915473
Otto E. Neugebauer (1975). "A History of Ancient Mathematical Astronomy". Birkhäuser: 577. ISBN 3-540-06995-X.