Attack on Titan

NASA announced last week that it had selected the Dragonfly mission to explore the prebiotic organic chemistry and look for signs of life on Titan. At 3,200 miles (5,150 km) across, Titan is the largest moon orbiting Saturn and the second-largest natural satellite in the Solar System. Larger than both the Moon and the planet Mercury.

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Because it is so far from the Sun, about 886 million miles (1.4 billion km), its surface temperature is minus 290 degrees Fahrenheit (minus 179 degrees Celsius). Its surface pressure is also 50% higher than Earth’s.

Titan has a dense, nitrogen-based atmosphere like Earth. Unlike Earth though, it has clouds and rain made of methane. The moon’s weather and surface processes have combined complex organics, energy, and water similar to those that may have sparked life on our planet. Other organics are formed in the atmosphere and fall like light snow.

The Mars rover-size, drone-like vehicle will have eight rotors and will fly to dozens of promising locations on Titan looking for prebiotic chemical processes common on both Titan and Earth.

Dragonfly will visit a world filled with a wide variety of organic compounds, which are the building blocks of life and could teach scientists about the origin of life itself. The rotorcraft will fly for miles across the organic sand dunes of Saturn’s largest moon, investigating the processes that shape Titan’s extraordinary environment.

It will take advantage of Titan’s dense atmosphere to become the first vehicle ever to fly its entire science payload to new places for repeatable and targeted access to surface materials.

During its 2.7-year baseline mission, Dragonfly will explore diverse environments from the organic dunes to the floor of an impact crater where liquid water and complex organic materials key to life once existed together for possibly tens of thousands of years.

Dragonfly is scheduled to launch in 2026 and reach Titan in 2034.

Well That’s Weird…

The South Pole-Aitken basin, the largest crater in the Solar System, is a gigantic impact structure on the far side of the Moon. Data from NASA’s lunar spacecraft points to the existence of a large excess of mass of about 2.18*1018 kg (about five times larger than the Big Island of Hawaii) in the lunar mantle underneath the basin. According to new research, this mass anomaly may contain metal from a massive asteroid that crashed into the Moon and formed the crater.

The South Pole-Aitken basin is oval-shaped, as 1,600 miles (2,500 km) wide and 8.1 miles (13 km) deep. Despite its size, it cannot be seen from Earth because, you know, it is on the far side of the Moon.

Researchers measured and analyzed small changes in the strength of gravity around the Moon, using data from NASA’s Gravity Recovery and Interior Laboratory (GRAIL) mission. When they combined that with lunar topography data from NASA’s Lunar Reconnaissance Orbiter, they discovered the unexpectedly large amount of mass hundreds of miles underneath the South Pole-Aitken basin.

The dense mass, whatever it is, wherever it came from, is weighing the basin floor downward by more than half a mile.

Computer simulations of large asteroid impacts suggest that, under the right conditions, an iron-nickel core of an asteroid may be dispersed into the lunar upper mantle during an impact.

The findings appear in the journal Geophysical Research Letters.

Moonquakes Too

In 2010, an analysis of images from NASA’s Lunar Reconnaissance Orbiter (LRO) found that the Moon shriveled like a raisin as its interior cooled, leaving behind thousands of cliffs called thrust faults on the lunar surface. A new analysis of archival data from seismometers deployed during the Apollo missions gives the first evidence that these thrust faults are still active and likely producing moonquakes today as the Moon continues to gradually cool and shrink.

Researchers found that a number of the quakes recorded in the Apollo data happened very close to the faults seen in the LRO imagery. The LRO images also show physical evidence of geologically recent fault movement, such as landslides and tumbled boulders.

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Astronauts placed five seismometers on the Moon’s surface during the Apollo 11, 12, 14, 15, and 16 missions. The Apollo 11 seismometer operated only for three weeks, but the four remaining instruments recorded 28 shallow moonquakes from 1969 to 1977. On Earth, the quakes would have ranged in magnitude from about 2 to 5.

Using the revised location estimates from their new algorithm, scientists found that the epicenters of eight of the 28 shallow quakes were within 19 miles of faults visible in the LRO images. This was close enough for the team to conclude that the faults likely caused the quakes.

The researchers also found that six of the eight quakes happened when the Moon was at or near its apogee, the point in the Moon’s orbit when it is farthest from Earth. This is where additional tidal stress from Earth’s gravity causes a peak in the total stress on the Moon’s crust, making slippage along the thrust faults more likely.

The LRO imaged more than 3,500 fault scarps on the Moon. Some of these images show landslides or boulders at the bottom of relatively bright patches on the slopes of fault scarps or nearby terrain. Brighter areas indicate regions that are freshly exposed by an event such as a moonquake.

Other LRO fault images show fresh tracks from boulder falls, suggesting that quakes sent these boulders rolling down their cliff slopes. Such tracks would be erased relatively quickly, in terms of geologic time, by the constant rain of micrometeoroid impacts on the Moon.

The study appears in the journal Nature Geoscience.

Hello From the Other Side

Looking up at the Moon, you might recognize familiar shadows and shapes on its face from one night to the next. We see the same view of the Moon our early ancestors did as it lighted their way after sundown.

Only one side of the Moon is ever visible from Earth, it wasn’t until 1959 when the Soviet Spacecraft Luna 3 orbited the Moon and sent pictures home that human beings were able to see the “far side” of the Moon for the first time.

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A phenomenon called tidal locking is responsible for the consistent view. The Earth and its Moon are in close proximity (relatively speaking) and thus exert significant gravitational forces on each other. These tidal forces slow the rotations of both bodies. This locked the Moon’s rotation in sync with its orbital period.

Now the Moon takes one trip around the Earth in the same amount of time it takes to make one rotation around its own axis: about 28 days. From Earth, we always see the same face of the Moon; from the Moon, the Earth stands still in the sky.

The near side of the Moon is well studied because we can see it. The astronauts landed on the near side of the Moon so they could communicate with NASA here on Earth. All of the samples from the Apollo missions are from the near side.

With modern satellites, astronomers have completely mapped the lunar surface. A Chinese mission, Chang’e 4, is currently exploring the Aitken Basin on the far side of the Moon, the first such mission ever landed there. Researchers hope Chang’e 4 will help answer questions about the crater’s surface features and test whether things can grow in lunar soil.

A privately funded Israeli mission, Beresheet, started as a mission to compete for the Google Lunar X Prize. Despite crashing during an attempted landing earlier this month, the Beresheet team still won the Moon Shot Award.

Being shielded from civilization means the far side of the moon is “radio dark.” There, researchers can measure weak signals from the universe that would otherwise be drowned out. Chang’e 4, for instance, will be able to observe low-frequency radio light coming from the Sun or beyond what’s possible to detect here on the Earth due to human activity, such as TV and radio broadcasts and other forms of communication signals. Low-frequency radio peers back in time to the very first stars and the very first black holes, giving astronomers a greater understanding of how the structures of the universe began forming.

Rover missions also investigate all sides of the Moon as space scientists prepare for future human missions, looking to the Moon’s resources to help humanity get to Mars. For instance, water, discovered by NASA’s LCROSS satellite beneath the Moon’s north and south poles in 2009, can be broken up into hydrogen and oxygen and used for fuel and breathing.