Weekend brings the eta Aquariid meteor shower on Earth, New Year on Mars

The eta Aquariid meteor shower peaks this weekend. Unfortunately, the weather doesn’t look very cooperative for prime viewing in the hours before sunrise Sunday morning. Fortunately, the eta Aquariids don’t have a very sharp peak in activity and meteors should be visible for the next few days.

The meteor shower is active between April 19 and May 28 as Earth passes through dust left by debris left when Haley’s comet last passed through our neighborhood.

The 4 a.m. hour Monday morning is expected to be the best time to see meteors with the setting waxing gibbous moon low on the horizon and nearly an hour of darkness remaining before twilight begins in a sky forecasted to be mostly cloud-free. Meteors can appear anywhere in the sky but will appear to originate from the constellation Aquarius as it rises in the East at 3 am.

Be sure to look for Saturn shining brightly in the South. In the west, a triangle will be brightly formed by the moon, Jupiter to the right and the star Spica on the left.

A few minutes before 8 am this morning, Raleigh time, Mars reached solar longitude 0 in its 687 day trip around our sun. This also marked the autumnal equinox in the southern hemisphere where the Mars rovers Curiosity and Opportunity make their way over the chilly landscape. Curiosity last reported a high temperature of 6 degrees Fahrenheit.

Cinco de Mayo 2017 also marks New Year’s day on Mars, beginning year 34.

Mars doesn’t have named months as we do here on Earth. Instead, its year is measured in 0-360 degrees of solar longitude (Ls). This is broken into the four seasons at Ls 0°, 90°, 180°, and 270°. Yes, Mars experiences seasons, because it has an axial tilt of 25 degrees very similar to Earth’s 23.5.

That longer year makes for longer seasons as well. On average Martian seasons, last 167 days compared to 91.5 here on Earth. Season length varies more on Mars because the eccentric orbit causes its orbital speed to vary. Autumn in the Mars southern hemisphere lasts the longest, 194 days. Spring is 52 days shorter.

The year number is arbitrary, based on a 2000 paper in the Journal of Geophysical Research studying the variability of temperatures and dust in the Mars atmosphere. They selected the Earth date of April 11, 1955, to begin Year one and Ls = 0 simply to enable year by year comparison in the paper. The convention stuck.

Each mission measures its longevity in Sols, or Martian days, beginning on its landing date. Each Sol lasts just shy of 24 hours, 40 minutes in Earth terms. On May 5, 2017, Curiosity entered Sol 1687 and Opportunity Sol 4721.