Flowing water on Mars, maybe not, this week on planetary radio.

Welcome, I'm at Kaplan of the Planetary Society with more of the human adventure across our solar system and beyond.

Recurring slope linee, RSLs.

They gave us hope that at least a little liquid water still makes it to the surface of the

red planet. A new paper says, think again. We'll talk with lead author of Colin Dundas of the U.S US Geological Survey, there's a mythic edition of

what's up ahead when we'll once again mix it up with Bruce Betts. Senior editor

Emily Loch Duvala is here for the start of our journey that takes us to a comet

and to Saturn's Moon Titan.

You may have heard us talk about NASA's three classes of missions.

The most ambitious and expensive are the flagships. The least expensive and supposedly

most frequent are discovery missions. In the middle are the new frontier's efforts, like the New Horizons Mission to Pluto and beyond. The frontier spacecraft. Emily, before you tell us about which of these two exciting missions may actually be headed out

across the solar system, I just got to say I'm selfish.

I wanted to see not just both of these but all the other missions that were up in this new

Frontiers program.

Oh don't we all Matt and I particularly have to shout out to my poor forsaken planet Venus that got shafted again in this choice.

No Venus mission selected, none in the last discovery round.

It's a planet we really need to understand. We need to understand why it's so different from Earth, even though it's made of the same stuff.

You know, we're discovering all these exoplanets that could be Venus-like or could be Earth-like, and if we don't know what makes our two Earth-sized planets

different then how are we ever going to understand exoplanets? All right,

Rantover. Our colleague Jason Davis who wrote about this new Frontiers

Down Select in a December 20th blog entry at planetary.org.

He actually includes some great tweet posts on this exact topic of Venus getting short shrift once again.

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