The longer pins are ground lines ("GND")...
Data:
![enter image description here](../../I/static/images/26187036b83af7ac94d85a41e1171b5157b9462a5c93e243fe66cabf071e6ae1.gif)
Power:
![enter image description here](../../I/static/images/2f02d0fb3636a442cbafce4e36ced79947749ce9dd152beb9ccaebdcccf6b3b0.jpg)
Ground lines are slightly longer than data/power lines on connectors that are intended to be regularly plugged/unplugged (especially in the case of hot-swap capable interfaces, like SATA) to ensure that the ground lines are being connected before any data/power lines are. This helps prevent electrical discharge into the device when attaching/removing it.
mSATA is an internal, clamp-down, 'permanent' connector type, so it's not intended to be "plugged" and "unplugged" regularly (by end users), and definitely not while the power is on. :)
1This is the same design as for USB cables. Take a look sometime. – phyrfox – 2015-12-31T21:50:43.540
1
Related: In which order do I plug the SATA power and data cables for hotplug? on [sf].
– a CVn – 2016-01-01T18:41:38.4001@phyrfox - interesting. Never noticed...also looks like Micro SD cards have same staggered hot plugging contacts. Interesting. – Carl B – 2016-01-02T00:52:43.827