MULTI-LEVEL MODELING OF PLUTO'S SURFACE AND ATMOSPHERE

Young, Buie, Young & Olkin

Multi-level modeling of Pluto's surface and atmosphere

Goal Understand Pluto, make predictions for the New Horizons

flyby, and position ourselves to capitalize on funding for Pluto research, which will be a hot topic for the next several years

Basic idea We have developed a new SwRI model of Pluto’s seasons,

which can be used in four papers with high impact. Big Picture

This will establish the dominance of our group in seasonal modeling of Pluto and other icy bodies, and interpretation of their visible, thermal, and infrared data.

Technical background

Transport of Volatile N2

Between surface and atmosphere

From summer to winter Observables

Visible appearance Temperatures Infrared (IR) spectra Time variation of these

quantities Context for New

Horizons

Role of volatile transport on Pluto

About a meter of N2 migrates each season.

Pressures vary by orders of magnitude over Pluto’s season. The history of atmospheric pressure depends critically on the location of the volatiles.

Volatile migration with albedo feedback probably explains why Pluto has extreme albedo contrasts.

VT3D example 1 of 3:Low thermal inertia, low N2 inventory

VT3D example 2 of 3:Low thermal inertia, larger N2 inventory

VT3D example 1 of 3:high thermal inertia, high N2 inventory

Proposal background

2010/2011: began numeric framework for three-dimensional volatile transport (VT3D)

2012: submitted first model description paper Young 2012: Volatile transport on inhomogeneous surfaces:

I – Analytic expressions, with application to Pluto’s day 2012: submited first data-driven paper

Young 2012, Pluto’s Seasons: New Predictions for New Horizons

Mostly compares modeled pressured with stellar occultation constraints on time variability of Pluto’s atmosphere

This work used minor funds from NASA Planetary Atmospheres, NASA Planetary Astronomy, Spitzer, New Horizons.

Work proposed here for 2013/2014

Apr-Jun 2013: submit VT3D paper & release code

Jul-Sep 2013: compare with visible data Oct-Dec 2013: compare with thermal

data Jan-Mar 2014: compare with infrared

data

Task 1: Disseminate VT3D model

Model Strengths Speed Accuracy Flexibility Visualization Wide

applicability to Pluto, Triton, and Kuiper-belt objects (KBOs)

Publish Model Release code

Task 2: Compare visible data & model Model

Color & albedo depends on terrain, age

Variation with latitude & longitude

Constraining Observations Albedo Color

Task 3: Compare thermal data & model Model

Emissivity depends on terrain, age, deposition rate

Variation with latitude & longitude

Observations Thermal

lightcurves vs. wavelength and year

Task 4: Compare infrared data & model Model

Spectra depends on terrain, age, temperature, deposition rate

Variation with latitude & longitude

Observations Spectra & band

depth vs. longitude and year

Timeline and milestones

Areas of risk and risk mitigation Risk: Competition by other volatile transport models

C. Hansen: revival of 1996 Pluto seasonal models F. Forget: volatile transport element in Global Climate

Models New work relating to the safety of New Horizons risks

delaying the completion of our models, which opens us up to the danger of being outstripped by others

Mitigation VT3D is faster and more flexible than competitors models. Use a mix of junior and senior scientists.

1 hour of senior per 5.5 hour of junior personnel Four well-defined, focused projects

Quick publication of high impact papers Make code publically available to dominate this field

Benefits to SwRI

Establish a competitive edge for SwRI Pluto scientists Develop and demonstrate state-of-the-art models Ensure high visibility

Capitalize on Pluto-related funding A specific NASA Pluto Data Analysis Program is planned Competition shows level of high importance and

interest of Pluto volatile transport Experience shows that spacecraft encounters generate

interest (and funding). We expect NASA, NSF, and telescope allocation committees will be favorably disposed to proposals to study Pluto and related objects (Triton and Kuiper-belt objects).