Travelers In The Night

Recently my Catalina Sky Survey teammates Carson Fuls and Greg Lenoard discovered an Aten asteroid which orbits the Sun once every 272 days and on a path that crosses the orbits of Venus and Earth a number of times each year. Atens account for only about 6% of the Earth approaching asteroids that asteroid hunters discover. They are relatively dim and difficult to discover because they spend most of their time inside the Earth's orbit with their sunlit side facing away from us. For example Carson and Greg's newly discovered asteroid, 2017 WJ16, is bright enough for asteroid hunters to track for only about 50 nights every couple of years. It is about 150 feet in diameter and travels on an orbit which can bring it to a bit more than three times the Moon's distance from Earth. When 2017 WJ16 is closer to the Sun than Earth it travels faster then we do allowing it to catch and just barely cross our orbit as we both travel about the Sun. In 2020, 2017 WJ16 will make one of it's closer approaches to us when it comes to about less than 5 times the Moon's distance from our home planet. At that time it will be traveling at 2.9 miles/second relative to us which is well within reach of our current rocket technology. I suspect that in the future if the pattern of colors which 2017 WJ16 reflects, reveals a high metal or water content humans will mine it to construct and operate their colonies in space.

According to NASA an average of one catalogued piece of space junk per day has come down to Earth over the past 50 years. Research is described which can track space junk in the atmosphere and provide the starting location and altitude for tracking clouds of environmentally problematic toxic chemical and/or nuclear contaminants released by the disintegration of reentering spacecraft.

The NASA Curiosity Rover has shown us evidence of ancient rivers and bodies of liquid water on the martian surface. Given it's thin cold atmosphere, seeps of liquid water, presently on the surface of Mars which are capable of hosting microbial life appear to be unlikely. Scientists were thus surprised when high resolution imaging of the red planet's surface revealed thousands of intriguing dark streaks called RSL on hundreds of rocky slope areas. These fascinating features slowly extend down hill and grow during the martian warm season, fade during the colder season, and reappear during the next martian warm period. On Earth features like these are produced by seeps of liquid water. However, on Mars a careful study of 151 RSL features at ten different sites using the high resolution camera on NASA's Mars Reconnaissance Orbiter reveal that they occur almost entirely on slopes which are greater than 27 degrees. This new research published in Nature Geoscience suggests that RSL are composed of solid particles in dry granular flows which unlike water seeps appear to end on many of the dunes when it's slope falls below a critical value. What makes RSL tick remains a mystery and likely involves small amounts of water trapped from the atmosphere. Currently surface conditions are hostile to life as we know it, however, the possibility of finding evidence of ancient life or perhaps even still existing microbe colonies in deep sub surface pockets of water are reasons to continue to explore our next door neighbor without contaminating it.

On a recent night my Catalina Sky Survey teammate Vivian Carvajal found 4 Earth approaching space rocks with our small but mighty Schmidt telescope on Mt. Bigelow, Arizona. These Earth approaching asteroids are all small with an average diameter about the width of tennis court. On their current paths none of them come closer than about 4 lunar distances from our home planet.

In 2012 as it crossed the orbit of Neptune heading towards the Sun a small space rock was 250 times fainter than can be detected by the Hubble Space Telescope. Five years later, after it had rounded the Sun, it became visible in asteroid hunter's telescopes for about 16 days, as it streaked across our planet's orbit at 37 miles per second, as it continued to move away from the Sun. During that brief period of time it was discovered by the PanSTARRS group in Hawaii, tracked by telescopes around the world, and given the name Oumuamua (“Oh-moo-ah-moo-ah”). Turns out that previous to the discovery observations, sightings too sparse to report, were obtained by my team using the Catalina Sky Survey's Schmidt telescope on Mt. Bigelow, Arizona. In 2024 this unusual space rock will cross Pluto's average distance from the Sun traveling on a path which will take it into deep interstellar space. Since we don't know how Oumuamua could obtained it's current trajectory from processes in our solar system, it is safe to presume that it originated in truly deep space. The mystery of Oumuamua deepened when astronomers measured it's brightness to change regularly by nearly 10 times over a 7.3 hour period of time. If these brightness variations are due to it's shape, and thus the amount of sun light reflected as it rotates, Oumuamua looks like a cigar. Even though Elon Musk's SpaceX Mars rocket could catch Oumuamua, it is more cost effective is to simply wait to discover another one of the several interstellar asteroids which pass by us each year.