The Crestone Eagle • April, 2021
Skies Over Crestone: April 2021
by Kim Malville
April 4: Last quarter moon
April 12: New moon
April 15-17: Watch the young crescent moon move through Taurus. First it will be near Aldebaran just after sunset. Look for the Pleiades to its lower right. On the next night the moon will be below Mars and then move above it on the 17th.
April 18: Catch the return of Venus as our Evening Star for the year, getting higher day by day, reaching its greatest height above the western horizon in early December
April 20: First quarter moon
April 27: Full moon
April 30: Some 20 minutes after sunset look to the west-northwest to catch Venus forming a line with the planet Mercury and the Pleiades.
Damselflies on Mars and Dragonflies on Titan
Last month we celebrated the landing on Perseverance on the surface of Mars. You may remember one of the more innovative features of this mission is the tiny autonomous helicopter known as Ingenuity, which hopefully will demonstrate the feasibility of powered flight in the thin atmosphere of Mars. The Red Planet’s gravity is about one-third that of Earth’s, but its atmosphere is just 1% the density of Earth’s, making its it harder to generate the lift required to get off the ground. Ingenuity is tiny and fragile, weighing only 4 lbs, hopefully light enough to achieve flight in the thin atmosphere of Mars. The goal of Perseverance is to search for evidence of life that may have existed when Mars was warmer and had water flowing in its veins. Perhaps some of you may remember The Martian Chronicles by Ray Bradbury and the sound of water in its imagined streams.
A similar rotorcraft is planned to reach Titan in next decade. Named Dragonfly, it will be huge compared to the Martian Ingenuity, weighing a whopping 1200 lbs. With eight whirling blades it will be a flying octopus, a true octocopter. With its low gravity, little wind, and dense atmosphere Titan is the most aerodynamically benign place in the solar system. Flying on Titan should be a piece of cake, some forty times easier than flying on the Earth. The atmosphere is four times denser than Earth’s and its gravity is only 14% that of the Earth. It will make it easier to fly, although it will be a cold piece of cake, with an average temperature of – 290o , some 200 degrees colder than the Pfizer vaccine.
Titan is the largest moon of Saturn and the second-largest moon in the Solar System after Jupiter’s Ganymede . It is the only moon known to have a dense atmosphere, and the only known body in space, other than Earth, where there is clear evidence of open bodies of liquid, that is liquid methane not liquid water.
Titan is 50% larger than our moon and larger than the planet Mercury. It was discovered in 1655 by the Dutch astronomer Christiaan Huygens, 45 years after Galileo discovered the four Galilean moons of Jupiter.
The atmosphere of Titan is largely nitrogen; minor components lead to the formation of methane and ethane clouds. Its climate—including wind and rain—creates surface features similar to those of Earth, such as dunes, rivers, lakes, and seas (probably of liquid methane and ethane), With its liquids and nitrogen atmosphere, Titan’s methane cycle bears a striking similarity to Earth’s hydrological but at a fiercely colder temperature.
Because methane exists as a liquid on Titan, it also evaporates and forms clouds, which occasionally causes methane rain. Clouds of methane ice and cyanide gas float over the moon’s surface and there are methane lakes with methane icebergs floating in them. It appears to have a liquid ocean beneath the surface that produces tides on the surface. Conditions on Titan could make the moon more habitable in the far future. If the sun increases its temperature (6 billion years from now) and becomes a red giant star, Earth could be uninhabitable and Titan’s temperature could increase enough for stable oceans to exist on the surface. If this happens, Titan could become our next home in the solar system.
The most recent speculations about life on Titan involve the organic hydrocarbons that coat its surface and its watery ocean underneath its 100km thick crust of ice. An asteroid or comet slamming into the moon could theoretically mix these two ingredients, according to a new study. The resulting impact craters could have provided an ideal place for life to get started. A temporary warm pool of warm water on the surface mixed with organic material cycling from the surface into the ocean makes conditions agreeable for the formation of life. Alvaro Penteado Crósta, a planetary geologist at the University of Campinas, Brazil, wondered whether any of the impact craters now on its surface were produced by impacts that were big enough to pierce the crust, bring water to the surface and dissolve the organic compounds on the surface, producing a primordial soup in which life could have developed. He and colleagues modeled the impact for the moon’s largest crater, 425-kilometer-wide Menrva, thought to have formed 1 billion years ago. Their model suggested the crater resulted from a 34-kilometer-wide space rock hitting the surface at 7 kilometers per second. That impact could have punctured the moon’s icy crust. The resulting lake inside the crater could have existed for 1 million years before freezing over and that may have been long enough time for microbes to evolve, taking advantage of liquid water, organic molecules, and heat from the impact.
NASA’s Dragonfly mission of an autonomous octocopter is set to launch in 2027 and arrive on Titan nine years later. If the impact an asteroid did break the ice crust on the moon, this mission could find evidence of ancient life. It will first land at the equatorial “Shangri-La” dune fields, which are similar to the linear dunes in Namibia in southern Africa, except they are not grains of silicon but beads of frozen organic compounds. Dragonfly will explore this region in short flights, building up to a series of longer “leapfrog” flights of up to 5 miles stopping along the way to take samples. It may reach the “Holy Grail” of an impact crater, where life may once have gained a precarious foothold in that ever so alien land.