Thursday, November 29, 2012

First to Venus: Mariner II

While one Soviet Venera spacecraft certainly passed near Venus prior to August of 1962, it was not successful in transmitting any data back to Earth... so Mariner II gets the credit for being the first successful probe to visit Venus.

Launched on August 27, 1962, Mariner II carried the following experiments intended for use at Venus (other instruments also took measurements of interplanetary space while enroute):

  • Microwave radiometer - meant to determine the temperature of the planet's surface and details concerning the atmosphere.
  • Infrared radiometer - meant to determine the structure of the cloud layer, and temperature distributions at cloud altitudes.
  • Magnetometer - meant to detect Venus' magnetic field

Mariner II arrived at its encounter point on December 14, almost four months after launch.  Never intended to enter orbit or plunge into the Venusian clouds, the spacecraft began recording as much information as it could in the short time Venus would be in range (the spacecraft was moving at 6.743 km/s relative to Venus).  A special command from Earth placed Mariner II  in "encounter" mode, during which it transmitted all recorded data in real time.  It passe within 34,854 km, and seven hours later, Mariner II returned to cruise mode to continue on in a heliocentric orbit.  Communication was lost on January 3, 1963.

So what did we learn about Venus from Mariner II?
  • The 19-mm microwave radiometer indicated roughly equal temperatures on the light and dark sides of the planet:
    • dark side =  460° K
    • terminator = 570° K
    • light side =  400° K
  • Near Venus, there was no indication of a magnetic field or of appreciable change in the solar plasma flux or the charged particle flux.
  • The infrared radiometer measured atmospheric temperatures that are consistent with Earth-based observations (hovering around 230° K), and detected no significant difference between the light and dark sides of the planet.
  • Mass of Venus: 4.87 x 10^24 kg (0.81485 of Earth)
Mariner II was successful by any measure, and set the stage for continued exploration of the inner solar system.  It was followed to Venus by a number of probes from the U.S., the Soviet Union, and the European Space Agency.  More to come!


Chase, S.C.; Kaplan, L.D.; Neugebauer, G. (1963) "The Mariner 2 Infrared Radiometer Experiment, Journal of Geophysical Research 68 (22): 6157–6169. (

NASA, Mariner-Venus 1962: Final Project Report, NASA SP-59, Washington, 1965 (

National Space Science Data Center: Mariner II. NASA web site (

Sonett, C. P. (1963). "A summary review of the scientific findings of the mariner venus mission." Space Science Reviews, 2(6), 751-777.

Thursday, November 15, 2012

Wandering Rogue Planet Is Really an Isolated Planetary Mass Object (IPMO)

IPMO known as CFBDSIR2149
Earlier this week, news outlets and Twitter were abuzz with recent news of a "rogue" and "orphaned" planet detected "wandering" through space a mere 100 light years from us.  I found this kind of reporting somewhat misleading, since it conjured images of a planet that was somehow flung out of orbit around its parent star, now left all alone in the cold... wandering... and even though the BBC article did a pretty good job of conveying some of the scientific conclusions, they still used quotes from the study's authors that sensationalized the "homeless planet" idea.

Reading the research paper that announced the discovery, CFBDSIR2149-0403: a 4-7 Jupiter-mass free-floating planet inthe young moving group AB Doradus ?, I got a somewhat different impression.

Philippe Delorme and his colleagues begin their report by questioning the dividing line between planets and star-like objects.  Currently, the Astronomical Union defines a planetary mass as one falling below the necessary minimum for thermonuclear fusion of deuterium (roughly 13 Jupiter masses), with brown dwarfs and stars above that line.  And while this new object weighs in far below that mass boundary and physically meets this criterion for a planet, there's more to the story.  It seems CFBDSIR2149 is tagging along with 30 or so young stars (similar in both age and composition) known as the AB Doradus Moving Group (ABDMG).  This association means it is likely about the same age and that it formed under similar circumstances.  For this reason, Delorme, et al. speculate that CFBDSIR2149 is an object resulting from stellar formation processes.  And even though its mass is insufficient to burn deuterium, it should not be classified as a planet.

What they think they know:  CFBDSIR2149 is a free-floating substellar object with a mass of 4-7 Jupiter masses, a surface tempurature of ~700K, and is likely a member of the AB Doradus group of stars that are between 50 ans 120 million years old.

Fun facts:
  • CFBDSIR stands for Canada-France Brown Dwarf Survey InfraRed
  • The authors find the probability that CFBDSIR2149 is a member of the ABDMG is 87%
  • They are continuing their parallax measurements of CFBDSIR2149 to confirm or deny its membership in the AB Doradus group (no doubt another paper will be forthcoming)

Tuesday, November 6, 2012

AcWriMo 2012 - My Commitment

Have you read about AcWriMo?  Yep, its a sort of National Novel Writing Month (NaNoWriMo) for academic writing.  I've decided to participate, and yes, I'm a little late to the game (It's already November 6).

This is where I make set a crazy goal: Complete a publishable (format and content, anyway) literature review of current thinking on astrobiological possibilities (past and present) for Venus by November 30.

Go Public: I just did with this blog post!

Strategy: Well, it's like writing anything, so there is a sequence for me:

  1. Collection: Find the published papers I will start with for the research.  This entails a lot of time with Google Scholar, RefWorks, and the SAO/NASA Astrophysics Data System.
  2. Reading.  just what it says, plus note-taking.
  3. Organization: Taking all of my notes and organizing them into the sections of the paper
  4. Writing.
There is a fair amount of rinse & repeat between steps 1 and 2, since good papers will lead me to others.  Even so, there is something to be written every day, almost from the beginning.

Discuss: I will.  I'll be posting here and on Twitter at @ElevenPointTwo.

What about Venus?

NASA Photo
Mars is getting a lot of attention lately.  Truth be told, Mars has been getting a lot attention for quite some time: landers, rovers, orbiters, and Elon Musk and President Obama want to send people there.  Mars One is creating a reality TV show to send contestants to the surface of Mars!

So what about Earth's "sister" planet?  Where's the love for Venus?  [This question is all the more ironic given that in Roman mythology, Venus was the goddess of love, beauty, sex, and all that.]

Well, I am not going to sit idly and do nothing.  I'm going to start giving Venus more of the attention it sorely deserves!  Here are some of my reasons:
  • Venus is right there every night (well, most nights)!  It's the second-brightest object in the night sky, and its phases can be observed with binoculars.
  • It is the closest-approaching planet to Earth (38 million kilometers at its closest)
  • It is roughly the same size and mass as Earth
  • It has an honest-to-goodness atmosphere
  • It possesses the most similar environment to Earth conditions in the solar system1
  • It may have harbored life in its early days
I've been interested in Venus for quite some time, and have always wanted to dig a little deeper into the subject.  Be careful what you wish for!  I'm currently taking a UND grad course in Astrobiology, and our final assignment is to write a literature review on an astrobiological subject.  I chose Venus, so it's going to be all Venus, all the time for me.

I'll do what I can to share interesting snippets here on the blog as I go, but I also plan to write some topical articles such as:
  • Robotic Missions to Venus: Past, Present
  • Robotic Missions to Venus: Proposed
  • The Case for Human Missions to Venus
  • Venus Facts You Should Know
Check back, I'll try to keep the material coming every week or so for a while.

1. This is not at the surface... it is about 50km up into the Venusian atmosphere.