Travelers In The Night

My Catalina Sky Survey teammate Greg Leonard was asteroid hunting with our 60 inch telescope on Mt. Lemmon, Arizona when he came across an unknown moving point of light in the night sky. After Greg reported his observations to the Minor Planet Center his discovery was tracked by telescopes in California, Romania, Germany, New Mexico, Arizona, Bavaria, and Japan. Astronomers used these data to calculate that Greg’s discovery orbits the sun between Venus and Earth , estimate its size to be approximately twice the length of a football field, and give it the name 2026 BX4. NASA classifies it to be a Potentially Hazardous Asteroid, however, since it doesn’t cross the Earth’s orbit it is not an immediate impact threat. In fact it will not come as close to us as it can on its current path until February 17, 2075 when it will pass less than 6 times the moon’s distance from us. Because 2026 BX4’s orbit is entirely within the Earth’s path about the Sun it is classified to be an Atira asteroid. These space rocks are difficult to discover and track because they are always near the Sun in the sky. 2026 BX4 could become an impact threat by gravitational interactions with Earth, Venus or another asteroid. There are also Aten asteroids which spend most of their time inside the Earth’s orbit but cross it and are more of a threat than an Atira asteroid like 2026 BX4. Currently the most dangerous Aten asteroid is Apophis which will safely pass closer to us than the communication satellites on Friday February 13, 2029. Asteroid hunters will continue to discover and track both Atira and Aten asteroids to make sure none of them sneak up on our home planet from the direction of the Sun.

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.