  X-rays from very young stars are powerful probes to investigate the
mechanisms at work in the very first stages of the star formation and the
origin of X-ray emission in very young stars. We present results from a 500 ks
long observation of the Rho Ophiuchi cloud with a XMM-Newton large program
named DROXO, aiming at studying the X-ray emission of deeply embedded Young
Stellar Objects (YSOs). The data acquired during the DROXO program were reduced
with SAS software, and filtered in time and energy to improve the signal to
noise of detected sources; light curves and spectra were obtained. We detected
111 sources, 61 of them associated with rho Ophiuchi YSOs as identified from
infrared observations with ISOCAM. Specifically, we detected 9 out of 11 Class
I, 31 out of 48 Class II and 15 out 16 Class III objects. Six objects out of 21
classified Class III candidates are also detected. At the same time we suggest
that 15 Class III candidates that remain undetected at log Lx < 28.3 are not
related to the cloud population. The global detection rate is ~64%. We have
achieved a flux sensitivity of ~5 x 10^{-15} erg s^{-1} cm^{-2}. The Lx to
L_bol ratio shows saturation at a value of ~ -3.5 for stars with T_eff <= 5000
K or 0.7 M_sun as observed in the Orion Nebula. The plasma temperatures and the
spectrum absorption show a decline with YSO class, with Class I YSOs being
hotter and more absorbed than Class II and III YSOs. In one star (GY 266) with
infrared counterpart in 2MASS and Spitzer catalogs we have detected a soft
excess in the X-ray spectrum which is best fitted by a cold thermal component
less absorbed than the main thermal component of the plasma. Such a soft
component hints to the presence of plasma heated by shocks due to jets outside
the dense circumstellar material.
