12/27/2021 – Ephemeris – Where did Earth’s water come from?

This is Ephemeris for Monday, December 27th. Today the Sun will be up for 8 hours and 49 minutes, setting at 5:08, and it will rise tomorrow at 8:19. The Moon, 1 day past last quarter, will rise at 2:02 tomorrow morning.

The element hydrogen has two stable forms: Ordinary hydrogen with a single proton as its nucleus, and deuterium with a proton and a neutron as its nucleus. Both can combine with oxygen to form water. Deuterium and oxygen make heavy water. Water of any kind would not have survived Earth’s formation. Astronomers have long thought that collisions of asteroids and comet brought water to the Earth. Comets, however, have an overabundance of deuterium. Asteroids are close, also dust particles exposed to the solar wind have an under abundance of deuterium. Apparently, about a 50-50 mixture of dust and asteroids appear the right combination to fill the Earth’s with the right ratio of normal and heavy water.

The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EST, UT – 5 hours). They may be different for your location.

Addendum

The three isotopes of hydrogen: protium, or ordinary hydrogen; deuterium; and tritium. Protium and deuterium are stable, while tritium is unstable and decays into helium 3 and an electron. Tritium has a half-life of 12.32 years.

Heavy water D₂O vs. normal water H₂O. Heavy water is about 11% heavier than water. A heavy water ice cube would sink in a glass of water.

06/19/2018 – Ephemeris – The Mars rover Opportunity is facing its greatest challenge

Ephemeris for Tuesday, June 19th. Today the Sun will be up for 15 hours and 34 minutes, setting at 9:31, and it will rise tomorrow at 5:57. The Moon, 1 day before first quarter, will set at 2:01 tomorrow morning.

The Mars Exploration Rover-B, named Opportunity landed on the Red Planet on January 25, 2004 for a mission hoping to last 90 Martian days or sols. It has been going strong for over 5,000 sols, or nearly 14 ½ Earth years, and has driven over 28 miles. Now Oppy, as its controllers affectionately call it, is meeting it’s greatest challenge. A huge dust storm, threatening to engulf the entire planet is building up. It has cut off the sunlight that power’s Oppy’s solar panels. Day has become night. The Jet Propulsion Laboratory controllers have put Oppy in deep sleep mode, powering only its clock to wait out the storm. They are awaiting Oppy’s phone home call scheduled for 11 a.m. at its local time each sol.

The times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.

Addendum

An animation of Mars global scans by the Mars Reconnaissance Orbiter over the period of May 31 to June 11, 2018. Two dust storms, one from the north, and another from the south converge and threaten to go global. Click on the image to enlarge. Credit: NASA/JPL-Caltech/MSSS.

Lights out for Oppy. The Sun photographed by Opportunity over several sols. Credit NASA/JPL-Caltech.

Below, the News Conference about Opportunity and the dust storm, recorded June 13, 2018.