Recent Studies of Mars: 2013-2014

Richard W. Schmude, Jr. Gordon State College

Barnesville, GA

Overview

• Purpose of work

• North Polar Cap (NPC) • Hellas

• Brightness measurements

Purpose

• NPC interannual variability

• Hellas variability– Time of day– Year– season

• Brightness (visible & Near infrared)

Hubble Image Processed by P. James, T. Clancy, S. Lee and NASA

Introduction: Ls

Ls range Season (N. hemisphere)0 – 90° Spring

90 – 180° Summer180 – 270° Fall

270 – 0° Winter

Voting Questions

• Do not talk to anyone until after 1st vote

• After 1st vote– Talk to someone that you disagree with– Convince him/her that you are right– Listen to your partner

Voting Question

• If Ls = 135° it is ___________ in the northern hemisphere.

a. late spring b. mid springc. early summer d. mid summer

Voting Question

Ls = 50° is similar to _______ in the USA.

a. February b. Junec. October d. May

Method and Materials

• WinJupos– Name an image• 2014-07-12-1320-name & other info.

– Load an image– Software computes longitude & latitude

Polar Cap MeasurementGoal: get all longitudes

NPC: Mean latitude

Hellas measurements

• Northern border measured– Every 5° of longitude– 270° W to 320° W– Red light images used– Mean values computed for each 5° of longitude

Why red light?green-left & red-right

Results: NPC in 2013 – 2014

Interannual variability

• Spring NPC – Mean latitudes (all longitudes) considered– Wilcoxon Signed Rank Test• 90% confidence level• As few as five values • Non-parametric test

Data sets

• MGS: 2000, 2002, 2006*, 2007-08*

• Schmude: 2009-10, 2011-12, 2013-14

• Individual latitudes are not reported

ResultsYear D mean latitude Comparison to 20002000 --- The standard2002 0.9° Larger2006 ~0.2° Probably the same

2007-08 ~0.6° Probably smaller2009-10 0.8° Larger2011-12 0.3° Same2013-14 0.0° Same

Voting Question

At Ls = 50°, the temperatures are __________ in the southern hemisphere of Mars.

a. rising b. falling

Hellas: white layer

• Northern border– Clouds or frost?– Growth during fall?– Changes from morning to afternoon?– Interannual differences?

Hellas: white layer

Hellas: changes in Northern border

• Wilcoxon Signed Rank Test– Mid fall (1995) and late fall – early winter (2014)– Morning afternoon (2014)– 2012 and 2014 (similar seasons)

Statistical results: Hellas

• There is no statistical difference (90% conf.)– Mid fall and late fall/early winter– Morning and afternoon– 2012 and 2014 (similar seasons)

Brightness Measurements

• Purpose– Long-term changes– Water reservoirs– Dust storms– Brightness model of planet

Brightness in Magnitudes

• Zero magnitude = a flux of light

• As magnitude drops, brightness increases

Electromagnetic Radiation

• Electric wave • Magnetic wave• Velocity = 186,000 miles/hour (vacuum)• Wavelength (length of one wave)

Electromagnetic radiationWavelength and color

Filter Wavelength ColorV 540 nm greenR 700 nm redJ 1250 nm noneH 1650 nm none

Previous work

• Schmude measured B, V, R and I brightness of Mars from 1991 to 2014

• Mallama (2007) summarizes work up to 2005.

• Almost no work done for J and H filters

Near Infrared light

Voting question

Please rank the objects from highest to lowest magnitude.

a. Sun, full Moon, Venusb. Sun, Venus, full Moonc. Full Moon, Venus, Sund. Venus, full Moon, Sun

Materials

• SSP-4 photometer• Celestron CG-4 mount• 0.09 m Maksutov telescope• Extension cord (requires AC power)

Experimental set-up

Method of brightness measurement

• Sky brightness and then comparison star• Sky brightness and then Mars• Repeat 2 ½ more times

• Compute Mars’ magnitude• Make corrections

Normalized Magnitude J(1,0) and H(1,0)

• Mars is 1 au from Earth and Sun

• Sunlight reflects directly back to observer (zero phase angle)

Results: Albedo

Light curve J filter

Light curve H filter

Conclusions

• NPC may undergo small changes from one year to the next

• Hellas white area: No change with respect to diurnal, seasonal or year to year cycles

• Mars’ albedo does not rise in near infrared

• Mars brightens as it rotates in the J & H filters